<SUBMISSION>
<ACCESSION-NUMBER>0001193125-14-150947
<TYPE>S-8 POS
<PUBLIC-DOCUMENT-COUNT>1
<FILING-DATE>20140421
<DATE-OF-FILING-DATE-CHANGE>20140422
<EFFECTIVENESS-DATE>20140421
<FILER>
<COMPANY-DATA>
<CONFORMED-NAME>AMERICAN PACIFIC CORP
<CIK>0000350832
<ASSIGNED-SIC>2810
<IRS-NUMBER>596490478
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>0930
</COMPANY-DATA>
<FILING-VALUES>
<FORM-TYPE>S-8 POS
<ACT>33
<FILE-NUMBER>333-176534
<FILM-NUMBER>14775381
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>3883 HOWARD HUGHES PARKWAY
<STREET2>STE 700
<CITY>LAS VEGAS
<STATE>NV
<ZIP>89169
<PHONE>7027352200
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>3883 HOWARD HUGHES PARKWAY
<STREET2>STE 700
<CITY>LAS VEGAS
<STATE>NV
<ZIP>89169
</MAIL-ADDRESS>
</FILER>
<DOCUMENT>
<TYPE>S-8 POS
<SEQUENCE>1
<FILENAME>d715773ds8pos.htm
<DESCRIPTION>S-8 POS
<TEXT>
<HTML><HEAD>
<TITLE>S-8 POS</TITLE>
</HEAD>
 <BODY BGCOLOR="WHITE">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>As filed with the Securities and Exchange Commission on April &nbsp;&nbsp;&nbsp;&nbsp;, 2014
</B></P> <P STYLE="font-size:4pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P> <P STYLE="line-height:1.0pt;margin-top:0pt;margin-bottom:0pt;border-bottom:1px solid #000000">&nbsp;</P>
<P STYLE="line-height:3.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000">&nbsp;</P> <P STYLE="margin-top:4pt; margin-bottom:0pt; font-size:18pt; font-family:Times New Roman" ALIGN="center"><B>UNITED STATES </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:18pt; font-family:Times New Roman" ALIGN="center"><B>SECURITIES AND EXCHANGE COMMISSION </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B>Washington,&nbsp;D.C. 20549 </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center>
<P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B>POST-EFFECTIVE AMENDMENT NO. 1 </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B>TO </B></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:18pt; font-family:Times New Roman" ALIGN="center"><B>FORM S-8</B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:14pt; font-family:Times New Roman" ALIGN="center"><B>REGISTRATION STATEMENT NO. 333-176534 </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:14pt; font-family:Times New Roman" ALIGN="center"><B>REGISTRATION STATEMENT NO. 333-153758 </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:14pt; font-family:Times New Roman" ALIGN="center"><B>REGISTRATION STATEMENT NO. 333-131945 </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B><I>UNDER </I></B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B><I>THE
SECURITIES ACT OF 1933 </I></B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center> <P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:24pt; font-family:Times New Roman" ALIGN="center"><B>American Pacific Corporation </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Exact name of registrant as specified in its charter) </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center>
<P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:8pt" ALIGN="center">


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<TD VALIGN="top" ALIGN="center"><B>Delaware</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><B>59-6490478</B></TD></TR>
<TR STYLE="font-family:Times New Roman; font-size:8pt">
<TD VALIGN="top" ALIGN="center"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>(State or other jurisdiction of</B></P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>incorporation or organization)</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>(IRS Employer</B></P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>Identification Number)</B></P></TD></TR>
</TABLE> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD VALIGN="top" ALIGN="center"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>3883 Howard Hughes Parkway, Suite 700</B></P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>Las Vegas, NV</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center"><B>89169</B></TD></TR>
<TR STYLE="font-family:Times New Roman; font-size:8pt">
<TD VALIGN="top" ALIGN="center"><B>(Address of principal executive offices)</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><B>(Zip code)</B></TD></TR>
</TABLE> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center> <P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>American Pacific Corporation Amended and Restated 2008 Stock Incentive Plan </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>American Pacific Corporation 401(k) Plan </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>AMPAC Fine Chemicals LLC Bargaining Unit 401(k) Plan </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>(Full title of the plan) </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>Dana M. Kelley </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>Vice
President, Chief Financial Officer and Treasurer </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>American Pacific Corporation </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>3883 Howard Hughes Parkway, Suite 700 </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>Las Vegas, NV 89169 </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>(Name
and address of agent for service) </B></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(702) 735-2200 </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>(Telephone number, including area code, of agent for service) </B></P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center> <P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><I>Copy to: </I></B></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>Zane
O. Gresham </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>Morrison&nbsp;&amp; Foerster LLP </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>425 Market Street </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>San
Francisco, CA 94105 </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(415)&nbsp;268-7000 </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center>
<P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Indicate by
check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of &#147;large accelerated filer,&#148; &#147;accelerated filer&#148; and
&#147;smaller reporting company&#148; in Rule 12b-2 of the Exchange Act. (Check one): </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TR>
<TD WIDTH="16%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="60%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="20%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="1%"></TD></TR>


<TR STYLE="font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom">Large&nbsp;accelerated&nbsp;filer</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"><FONT STYLE="FONT-FAMILY:WINGDINGS">&#168;</FONT></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">Accelerated&nbsp;filer</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"><FONT STYLE="FONT-FAMILY:WINGDINGS">&#120;</FONT></TD></TR>
<TR>
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom">Non-accelerated filer</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"><FONT STYLE="FONT-FAMILY:WINGDINGS">&#168;</FONT>&nbsp;&nbsp;(Do not check if a smaller reporting company)</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">Smaller&nbsp;reporting&nbsp;company</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"><FONT STYLE="FONT-FAMILY:WINGDINGS">&#168;</FONT></TD></TR>
</TABLE> <P STYLE="font-size:10pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P> <P STYLE="line-height:1.0pt;margin-top:0pt;margin-bottom:0pt;border-bottom:1px solid #000000">&nbsp;</P>
<P STYLE="line-height:3.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000">&nbsp;</P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>EXPLANATORY NOTE </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">This Post-Effective Amendment No.&nbsp;1 relates to the following Registration Statements on Form S-8 (collectively, the &#147;Registration
Statements&#148;) of American Pacific Corporation (the &#147;Company&#148;): </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TR>
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top">File No.&nbsp;333-176534, pertaining to the registration of 450,000 shares of Common Stock, $0.10 par value per share, of the Company (the &#147;Common Stock&#148;), issuable under the American Pacific Corporation
Amended and Restated 2008 Stock Incentive Plan, and the associated preference share purchase right and associated rights to purchase Common Stock (collectively, &#147;Common Stock Purchase Rights&#148;) described in the Registration Statement;
</TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top">File No.&nbsp;333-153758, pertaining to the registration of 400,000 shares of Common Stock issuable pursuant to the American Pacific Corporation 401(k) Plan, the associated Common Stock Purchase Rights and an
indeterminate amount of interests to be offered or sold pursuant to such plan; and </TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top">File No.&nbsp;333-131945, pertaining to the registration of 300,000 shares of Common Stock issuable pursuant to the AMPAC Fine Chemicals LLC Bargaining Unit 401(k) Plan, the associated Common Stock Purchase Rights and
an indeterminate amount of interests to be offered or sold pursuant to such plan. </TD></TR></TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">On February&nbsp;27, 2014, pursuant to
the Agreement and Plan of Merger, dated as of January&nbsp;9, 2014, by and between Flamingo Parent Corp., a Delaware corporation (&#147;Parent&#148;), and Flamingo Merger Sub Corp., a Delaware corporation and a wholly owned subsidiary of Parent,
both of which are affiliates of and controlled by H.I.G. Capital, LLC, a Delaware limited liability company (&#147;H.I.G.&#148;), the Company became a wholly owned portfolio company of H.I.G. (the &#147;Merger&#148;). </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">As a result of the Merger, the offerings pursuant to the Registration Statements have been terminated. In accordance with undertakings made by
the Company in the Registration Statements to remove from registration, by means of a post-effective amendment, any securities of the Company which remain unsold at the termination of the offerings, the Company hereby files this Post-Effective
Amendment No.&nbsp;1 to remove from registration all of the securities described above that were registered but unsold under the Registration Statements as of the date hereof, if any. </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>SIGNATURES </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Pursuant to the requirements of the Securities Act of 1933, as amended, the registrant certifies that it has reasonable grounds to believe
that it meets all of the requirements for filing on Form S-8 and has duly caused this Post-Effective Amendment No.&nbsp;1 to the Registration Statements on Form S-8 to be signed on its behalf by the undersigned, thereunto duly authorized, in the
City of Las Vegas, State of Nevada, on April&nbsp;21, 2014. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><DIV ALIGN="right">
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<TD VALIGN="top" COLSPAN="3"><B>American Pacific Corporation</B></TD></TR>
<TR>
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="bottom"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">/s/ DANA M. KELLEY</P></TD></TR>
<TR STYLE="font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">Name:</TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="bottom">Dana M. Kelley</TD></TR>
<TR STYLE="font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">Title:</TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="bottom">Vice President, Chief Financial Officer and Treasurer</TD></TR>
</TABLE></DIV> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Note: No other person is required to sign this post-effective amendment to the Registration Statements on Form S-8 in
reliance on Rule 478 of the Securities Act of 1933, as amended. </P>
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