<SUBMISSION>
<ACCESSION-NUMBER>0001104659-05-017960
<TYPE>8-K
<PUBLIC-DOCUMENT-COUNT>3
<PERIOD>20050425
<ITEMS>8.01
<ITEMS>9.01
<FILING-DATE>20050426
<DATE-OF-FILING-DATE-CHANGE>20050425
<FILER>
<COMPANY-DATA>
<CONFORMED-NAME>AEROGEN INC
<CIK>0001039160
<ASSIGNED-SIC>3841
<IRS-NUMBER>330488580
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<FILING-VALUES>
<FORM-TYPE>8-K
<ACT>34
<FILE-NUMBER>000-31913
<FILM-NUMBER>05771381
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>2071 STIERLIN COURT
<CITY>MOUNTAIN VIEW
<STATE>CA
<ZIP>94043
<PHONE>650 864-7300
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>2071 STIERLIN COURT
<CITY>MOUNTAIN VIEW
<STATE>CA
<ZIP>94043
</MAIL-ADDRESS>
</FILER>
<DOCUMENT>
<TYPE>8-K
<SEQUENCE>1
<FILENAME>a05-7286_18k.htm
<DESCRIPTION>8-K
<TEXT>
<html>

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</head>

<body lang="EN-US" link="blue" vlink="purple" style="text-justify-trim:punctuation;">

<div style="font-family:Times New Roman;">

<div style="border:none;border-top:double windowtext 9.0pt;padding:0in 0in 0in 0in;">

<p style="border:none;margin:0in 0in .0001pt;padding:0in;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

</div>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="5" face="Times New Roman" style="font-size:18.0pt;font-weight:bold;">UNITED
STATES</font></b></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="5" face="Times New Roman" style="font-size:18.0pt;font-weight:bold;">SECURITIES
AND EXCHANGE COMMISSION</font></b></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Washington,
D. C.&nbsp; 20549</font></b></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="5" face="Times New Roman" style="font-size:18.0pt;font-weight:bold;">FORM 8-K</font></b></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="3" face="Times New Roman" style="font-size:12.0pt;font-weight:bold;">CURRENT
REPORT</font></b></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="3" face="Times New Roman" style="font-size:12.0pt;font-weight:bold;">Pursuant
to Section&nbsp;13 or 15(d) of the</font></b></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="3" face="Times New Roman" style="font-size:12.0pt;font-weight:bold;">Securities
Exchange Act of 1934</font></b></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Date of Report (Date of
earliest event reported):&nbsp;<b><font style="font-weight:bold;"> April 25,
2005</font></b></font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="5" face="Times New Roman" style="font-size:18.0pt;font-weight:bold;">AEROGEN,
INC.</font></b></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(Exact name of registrant
as specified in its charter)</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Delaware</font></b></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(State or other
jurisdiction of incorporation)</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<table border="0" cellspacing="0" cellpadding="0" width="100%" style="border-collapse:collapse;width:100.0%;">
 <tr>
  <td width="49%" valign="top" style="padding:0in 0in 0in 0in;width:49.0%;">
  <p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">0-31913</font></b></p>
  </td>
  <td width="2%" valign="bottom" style="padding:0in 0in 0in 0in;width:2.0%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:1.0pt;font-weight:bold;">&nbsp;</font></b></p>
  </td>
  <td width="49%" valign="top" style="padding:0in 0in 0in 0in;width:49.0%;">
  <p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">33-0488580</font></b></p>
  </td>
 </tr>
 <tr>
  <td width="49%" valign="top" style="padding:0in 0in 0in 0in;width:49.0%;">
  <p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(Commission File No.)</font></p>
  </td>
  <td width="2%" valign="bottom" style="padding:0in 0in 0in 0in;width:2.0%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>
  </td>
  <td width="49%" valign="top" style="padding:0in 0in 0in 0in;width:49.0%;">
  <p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(IRS Employer
  Identification No.)</font></p>
  </td>
 </tr>
</table>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">2071
Stierlin Court, Suite 100</font></b></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Mountain
View, CA 94043</font></b></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(Address of principal
executive offices and zip code)</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Registrant&#146;s telephone
number, including area code:<b><font style="font-weight:bold;">
(650)&nbsp;864-7300</font></b></font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Check the appropriate box below if the Form 8-K filing is intended to
simultaneously satisfy the filing obligation of the registrant under any of the
following provisions (see General Instruction A.2. below):</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="font-size:10.0pt;margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Wingdings" style="font-size:10.0pt;">o</font>
Written communications pursuant to Rule 425 under the Securities Act (17 CFR
230.425)</p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="font-size:10.0pt;margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Wingdings" style="font-size:10.0pt;">o</font>
Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR
240.14a-12)</p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="font-size:10.0pt;margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Wingdings" style="font-size:10.0pt;">o</font>
Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange
Act (17 CFR 240.14d-2(b))</p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="font-size:10.0pt;margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Wingdings" style="font-size:10.0pt;">o</font>
Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange
Act (17 CFR 240.13e-4(c))</p>

<div style="border:none;border-bottom:double windowtext 9.0pt;padding:0in 0in 0in 0in;">

<p style="border:none;margin:0in 0in .0001pt;padding:0in;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

</div>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<div style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">

<hr size="2" width="100%" noshade color="gray" align="left">

</font></div>

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<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Item 8.01&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; Other Events.</font></b></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">On April 25, 2005, Aerogen (the &#147;Company&#148;) issued a
press release announcing that the 2004 audited financial statements were
subject to a going concern qualification.</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&#160;<b><font style="font-weight:bold;">Item 9.01.&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; Financial
Statements and Exhibits.</font></b></font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(c)&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; Exhibits:</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">99.1&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; Press Release, dated
April 25, 2005, entitled &#147;Aerogen 2004 Audited Financial Statements Subject to
Going Concern Qualification.&#148;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">2</font></p>

<div style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">

<hr size="2" width="100%" noshade color="gray" align="left">

</font></div>

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<div style="font-family:Times New Roman;">

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">SIGNATURE</font></b></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Pursuant to the requirements of the Securities Exchange Act of 1934,
the registrant has duly caused this report to be signed on its behalf by the
undersigned, thereunto duly authorized.</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<table border="0" cellspacing="0" cellpadding="0" width="100%" style="border-collapse:collapse;width:100.0%;">
 <tr>
  <td width="60%" valign="top" style="padding:0in 0in 0in 0in;width:60.18%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>
  </td>
  <td width="39%" colspan="4" valign="top" style="padding:0in 0in 0in 0in;width:39.82%;">
  <p style="font-size:10.0pt;margin:0in 0in .0001pt;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">AEROGEN</font></b>,<b><font style="font-weight:bold;"> INC.</font></b></p>
  </td>
 </tr>
 <tr>
  <td width="60%" valign="top" style="padding:0in 0in 0in 0in;width:60.18%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">&nbsp;</font></b></p>
  </td>
  <td width="6%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:6.08%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">&nbsp;</font></b></p>
  </td>
  <td width="33%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:33.74%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">&nbsp;</font></b></p>
  </td>
 </tr>
 <tr>
  <td width="60%" valign="top" style="padding:0in 0in 0in 0in;width:60.18%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">&nbsp;</font></b></p>
  </td>
  <td width="6%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:6.08%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">&nbsp;</font></b></p>
  </td>
  <td width="33%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:33.74%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">&nbsp;</font></b></p>
  </td>
 </tr>
 <tr>
  <td width="60%" valign="top" style="padding:0in 0in 0in 0in;width:60.18%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Dated:&nbsp; April 25, 2005</font></p>
  </td>
  <td width="4%" valign="top" style="padding:0in 0in 0in 0in;width:4.4%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">By:</font></p>
  </td>
  <td width="25%" colspan="2" valign="top" style="border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 0in 0in;width:25.24%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">/s/ Robert S. Breuil</font></p>
  </td>
  <td width="10%" valign="top" style="padding:0in 0in 0in 0in;width:10.18%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>
  </td>
 </tr>
 <tr>
  <td width="60%" valign="top" style="padding:0in 0in 0in 0in;width:60.18%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:1.0pt;font-weight:bold;">&nbsp;</font></b></p>
  </td>
  <td width="6%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:6.08%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Name:</font></p>
  </td>
  <td width="33%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:33.74%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;Robert S. Breuil</font></p>
  </td>
 </tr>
 <tr>
  <td width="60%" valign="top" style="padding:0in 0in 0in 0in;width:60.18%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:1.0pt;font-weight:bold;">&nbsp;</font></b></p>
  </td>
  <td width="6%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:6.08%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Title:</font></p>
  </td>
  <td width="33%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:33.74%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Chief Financial Officer and Vice</font></p>
  </td>
 </tr>
 <tr>
  <td width="60%" valign="top" style="padding:0in 0in 0in 0in;width:60.18%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>
  </td>
  <td width="6%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:6.08%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>
  </td>
  <td width="33%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:33.74%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">President of Corporate Development</font></p>
  </td>
 </tr>
 <tr height="0">
  <td width="450" style="border:none;"></td>
  <td width="33" style="border:none;"></td>
  <td width="13" style="border:none;"></td>
  <td width="176" style="border:none;"></td>
  <td width="76" style="border:none;"></td>
 </tr>
</table>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">3</font></p>

<div style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">

<hr size="2" width="100%" noshade color="gray" align="left">

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<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">EXHIBITS</font></b></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">99.1&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; Press Release, dated
April 25, 2005, entitled &#147;Aerogen 2004 Audited Financial Statements Subject to
Going Concern Qualification.&#148;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">4</font></p>

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<TYPE>EX-99.1
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<p align="right" style="margin:0in 0in .0001pt;text-align:right;text-autospace:none;text-indent:.5in;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Exhibit
99.1</font></b></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman"><img width="103" height="61" src="g72861mmimage001.jpg"></font></p>

<h2 style="font-weight:bold;margin:0in 0in .0001pt;page-break-after:avoid;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></b></h2>

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<table border="0" cellspacing="0" cellpadding="0" width="100%" style="border-collapse:collapse;width:100.0%;">
 <tr>
  <td width="8%" valign="top" style="padding:0in 0in 0in 0in;width:8.16%;">
  <h2 style="font-weight:bold;margin:0in 0in .0001pt;page-break-after:avoid;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;">Contact:</font></b></h2>
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  <td width="91%" valign="top" style="padding:0in 0in 0in 0in;width:91.84%;">
  <h2 style="font-weight:bold;margin:0in 0in .0001pt;page-break-after:avoid;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;">Jane E. Shaw, Ph.D.</font></b></h2>
  </td>
 </tr>
 <tr>
  <td width="8%" valign="top" style="padding:0in 0in 0in 0in;width:8.16%;">
  <p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:1.0pt;font-weight:bold;">&nbsp;</font></b></p>
  </td>
  <td width="91%" valign="top" style="padding:0in 0in 0in 0in;width:91.84%;">
  <p style="margin:0in 0in .0001pt;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">(650)
  864-7333</font></b></p>
  </td>
 </tr>
</table>

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<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">AEROGEN 2004 AUDITED FINANCIAL STATEMENTS SUBJECT TO
GOING CONCERN QUALIFICATION</font></b></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">MOUNTAIN VIEW, CA, April 25, 2005</font></b><font size="2" style="font-size:10.0pt;"> &#151; Aerogen,
Inc. (Nasdaq AEGN) today announced that the report of the Company&#146;s independent
registered public accounting firm on Aerogen&#146;s 2004 financial statements,
included in the Company&#146;s Annual Report on Form 10-K/A filed on April 19, 2005,
contains an explanatory paragraph with respect to the Company&#146;s ability to
continue as a going concern.&#160; As stated
in the report, the Company has suffered recurring losses and negative cash
flows from operations that raise substantial doubt about the Company&#146;s ability
to continue as a going concern. Additional information regarding the Company&#146;s
liquidity and management plans can be found in the Form 10-K/A.</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">This
press release is being issued in compliance with Nasdaq Marketplace Rule
4350(b)(1)(B), which requires all listed companies to make a public
announcement through the news media after receiving an audit opinion that
incorporates a going concern qualification.</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Aerogen, a specialty
pharmaceutical company, develops products based on its OnQ<sup>&#174;</sup> Aerosol
Generator technology to improve the treatment of respiratory disorders in the
acute care setting.&#160; Aerogen has
presented the results of its first Phase 2 clinical study evaluating delivery
of aerosolized amikacin for the treatment of ventilator-associated pneumonia;
an additional Phase 2 study is currently underway.&#160; Following amikacin, additional drug products
targeting improved respiratory therapy in the acute care setting are in the
feasibility and pre-clinical stages of development.&#160; Aerogen&#146;s Aeroneb<sup>&#174;</sup> Professional
Nebulizer System is marketed world-wide for use in hospitals.&#160; Aerogen&#146;s Aeroneb<sup>&#174;</sup> Go Nebulizer
for home use is currently marketed in the U.S., Japan and certain European
countries.&#160; Aerogen also has development
collaborations with pharmaceutical and biotechnology companies for use of its
technology in the delivery of novel compounds that treat respiratory and other
disorders.&#160; Aerogen is headquartered in
Mountain View, California, with a campus in Galway, Ireland. For more
information, visit www.aerogen.com.</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-indent:.5in;"><i><font size="2" face="Times New Roman" style="font-size:10.0pt;font-style:italic;">To the extent any statements made in this release relate to
information that is not historical, these statements are necessarily
forward-looking. As such, they are subject to the occurrence of many events
outside of Aerogen&#146;s control and other uncertainties, and are subject to
various risk factors that could cause Aerogen&#146;s actual results to differ
materially from those expressed in any forward-looking statement.&#160; The risk factors include, without limitation,
the need for additional funding, evaluation of strategic alternatives,, the inherent
risks of product development, clinical outcomes, regulatory risks and risks
related to proprietary rights, market acceptance and competition, and are
described in Aerogen&#146;s reports and other filings with the U.S. Securities and
Exchange Commission, including Aerogen&#146;s Annual Report on Form 10-K for the
year ended December 31, 2004, filed with the Securities and Exchange Commission
(&#147;SEC&#148;) on April 15, 2005, as amended on April 19, 2005.&#160; Aerogen does not undertake any obligation to
update forward-looking statements.</font></i></p>

<p align="center" style="line-height:normal;margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">###</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<div style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">

<hr size="2" width="100%" noshade color="gray" align="left">

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