EXHIBIT 32.1

The following certifications are being furnished solely to accompany the Report pursuant to 18 U.S.C. § 1350 and in accordance with SEC Release No. 33-8238. These certifications shall not be deemed
filed for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, nor shall they be incorporated by reference in any filing of the Company under the Securities Act of 1933, as amended, whether made before or after
the date hereof, regardless of any general incorporation language in such filing.

Certification of Principal Executive Officer

Pursuant to 18 U.S.C. § 1350, as created by Section 906 of the Sarbanes-Oxley Act of 2002, the undersigned officer of
Peplin, Inc., a Delaware corporation (the Company), hereby certifies, to his knowledge, that:



|(i) | the accompanying Quarterly Report on Form 10-Q of the Company for the period ended March 31, 2009 (the Report) fully complies with the requirements of
Section 13(a) or Section 15(d), as applicable, of the Securities Exchange Act of 1934, as amended; and
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|(ii) | the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.
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/S/ THOMAS WIGGANSThomas WiggansChairman of the Board andChief Executive Officer(Principal Executive Officer)


Date: May 15, 2009

A signed original of this written statement required by Section 906 has been provided to Peplin, Inc. and will be retained by Peplin, Inc. and furnished to the Securities and Exchange Commission or its staff upon
request.

Certification of Principal Financial Officer

Pursuant to 18 U.S.C. § 1350, as created by Section 906 of the Sarbanes-Oxley Act of 2002, the undersigned officer of Peplin, Inc., a Delaware corporation (the Company), hereby certifies, to his
knowledge, that:



|(i) | the accompanying Quarterly Report on Form 10-Q of the Company for the period ended March 31, 2009 (the Report) fully complies with the requirements of
Section 13(a) or Section 15(d), as applicable, of the Securities Exchange Act of 1934, as amended; and
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|(ii) | the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.
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/S/ DAVID J. B. SMITHDavid J. B. Smith,Chief Financial Officer(Principal Financial Officer)


Date: May 15, 2009

A signed original of this written statement required by Section 906 has been provided to Peplin, Inc. and will be retained by Peplin, Inc. and furnished to the Securities and Exchange Commission or its staff upon
request.