<SUBMISSION>
<ACCESSION-NUMBER>0001237899-04-000002
<TYPE>5
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20031231
<FILING-DATE>20040106
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>GILMAN ALFRED G
<CIK>0001225473
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>5
<ACT>34
<FILE-NUMBER>000-19034
<FILM-NUMBER>04507831
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>DEPT OF PHARMACOLOGY K5 YUVER OF TEXAS
<STREET2>5323 HARRY HINES BLVD
<CITY>DALLAS
<STATE>TX
<ZIP>75390
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>REGENERON PHARMACEUTICALS INC
<CIK>0000872589
<ASSIGNED-SIC>2834
<IRS-NUMBER>133444607
<STATE-OF-INCORPORATION>NY
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>777 OLD SAW MILL RIVER RD
<CITY>TARRYTOWN
<STATE>NY
<ZIP>10591-6707
<PHONE>9143477000
</BUSINESS-ADDRESS>
</ISSUER>
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    <ownerSignature>
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</ownershipDocument>

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</SUBMISSION>
