As filed with the Securities and Exchange Commission on March 30, 2006

Registration No. 333-            

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-8

REGISTRATION STATEMENT

Under

The Securities Act of 1933

KOSAN BIOSCIENCES INCORPORATED

(Exact name of Registrant as specified in its charter)

Delaware	94-3217016
(State of incorporation)	(I.R.S. Employer Identification Number)

3832 Bay Center Place

Hayward, CA 94545

(510) 732-8400

(Address of principal executive offices)

1996 STOCK OPTION PLAN

2000 NON-EMPLOYEE DIRECTOR STOCK OPTION PLAN

2000 EMPLOYEE STOCK PURCHASE PLAN

(Full title of the plans)

Robert G. Johnson, Jr., M.D., Ph.D.

Chief Executive Officer

Kosan Biosciences Incorporated

3832 Bay Center Place

Hayward, CA 94545

(510) 732-8400

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copy to:

Suzanne Sawochka Hooper, Esq.

COOLEY GODWARD LLP

Five Palo Alto Square

3000 El Camino Real

Palo Alto, CA 94306

(650) 843-5000

CALCULATION OF REGISTRATION FEE

Title of Each Class of Securities to be Registered	Amount to be Registered (1)	Proposed Maximum Offering Price Per Share (2)		Proposed Maximum Aggregate Offering Price (2)		Amount of Registration Fee
Stock options and common stock (par value $.001 per share)	500,000 shares	$	5.875	$	2,937,500	$	314.31

(1) Pursuant to Rule 416(a) under the Securities Act of 1933, as amended (the “Securities Act”), this registration statement shall also cover any additional shares of Kosan’s common stock that become issuable under the 1996 Stock Option, 2000 Non-Employee Director Stock Option Plan, 2000 Employee Stock Purchase Plan by reason of any stock dividend, stock split, recapitalization or other similar transaction effected without Kosan’s receipt of consideration that results in an increase in the number of Kosan’s outstanding shares of common stock.

(2) Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rule 457(c) and (h)(l) under the Securities Act. The offering price per share and aggregate offering price for the unissued stock options and common stock are based upon the average of the high and low prices of Kosan’s common stock as reported on The Nasdaq National Market on March 27, 2006.

EXPLANATORY NOTE

This Registration Statement on Form S-8 is being filed for the purpose of registering (i) an additional 250,000 shares of common stock of Kosan Biosciences Incorporated (“Kosan”) to be issued pursuant to options under Kosan’s 1996 Stock Option Plan, as amended, (ii) an additional 100,000 shares of common stock of Kosan to be issued pursuant to options under Kosan’s 2000 Non-Employee Director Stock Option Plan, (iii) an additional 150,000 shares of common stock of Kosan to be issued pursuant to Kosan’s 2000 Employee Stock Purchase Plan.

INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

The contents of the Registration Statement on Form S-8 (relating to the 1996 Stock Option Plan, 2000 Employee Stock Purchase Plan and 2000 Non-Employee Director Stock Option Plan) File No. 333-47758, the Registration Statements on Form S-8 (relating to the 1996 Stock Option Plan) File Nos. 333-63534 and 333-96669, the Registration Statement on Form S-8 (relating to the 1996 Stock Option Plan and 2000 Employee Stock Purchase Plan) File No. 333-108502, the Registration Statement on Form S-8 (relating to the 1996 Stock Option Plan) File No. 333-115766 and the Registration Statement on Form S-8 (relating to the 1996 Stock Option Plan, 2000 Employee Stock Purchase Plan and 2000 Non-Employee Director Stock Option Plan) File No. 333-123578, previously filed with the Securities and Exchange Commission on October 11, 2000, June 21, 2001, July 18, 2002, September 4, 2003, May 21, 2004 and March 25, 2005, respectively, are incorporated by reference herein.

EXHIBITS

Exhibit Number	Description
5.1	Opinion of Cooley Godward LLP.
23.1	Consent of Independent Registered Public Accounting Firm.
23.2	Consent of Cooley Godward LLP. Reference is made to Exhibit 5.1.
24.1	Power of Attorney (contained on the signature page).
99.1(1)	1996 Stock Option Plan, as amended.
99.2(1)	2000 Non-Employee Director Stock Option Plan.
99.3(1)	2000 Employee Stock Purchase Plan.

(1) Incorporated herein by reference to an exhibit to the Registrant’s Statement on Form S-1, as amended (No. 333-33732), declared effective on October 4, 2000.

UNDERTAKINGS

1. The undersigned registrant hereby undertakes:

(a) To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

(i) To include any prospectus required by section 10(a)(3) of the Securities Act of 1933;

(ii) To reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Commission pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than 20% change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement.

(iii) To include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement;

Provided, however, that paragraphs (a)(i) and (a)(ii) do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the Commission by the registrant pursuant to section 13 or section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference herein.

(b) That, for the purpose of determining any liability under the Securities Act of 1933, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered herein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(c) To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

(d) That, for the purpose of determining liability of the registrant under the Securities Act of 1933 to any purchaser in the initial distribution of the securities, the undersigned registrant undertakes that in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

(i) Any preliminary prospectus or prospectus of the undersigned registrant relating to the offering required to be filed pursuant to Rule 424;

(ii) Any free writing prospectus relating to the offering prepared by or on behalf of the undersigned registrant or used or referred to by the undersigned registrant;

(iii) The portion of any other free writing prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of the undersigned registrant; and

(iv) Any other communication that is an offer in the offering made by the undersigned registrant to the purchaser.

2. The undersigned registrant hereby undertakes that, for purposes of determining any liability under the Securities Act of 1933, each filing of the registrant’s annual report pursuant to section 13(a) or section 15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to section 15(d) of the Securities Exchange Act of 1934) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered herein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

3. Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant

has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Act and will be governed by the final adjudication of such issue.

SIGNATURES

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 registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Hayward, State of California, on March 30, 2006.

KOSAN BIOSCIENCES INCORPORATED
By:	/s/ Robert G. Johnson, Jr.
	Robert G. Johnson, Jr., M.D., Ph.D.
	Chief Executive Officer

POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below constitutes and appoints Robert G. Johnson, Jr. and Margaret A. Horn, and each or any one of them, his or her true and lawful attorney-in-fact and agent, with full power of substitution and resubstitution, for him or her and in his or her name, place and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments) to this Registration Statement, and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in connection therewith, as fully to all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents, or any of them, or their or his or her substitutes or substitute, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, as amended, this registration statement has been signed on March 30, 2006 by the following persons in the capacities indicated:

Signature	Title	Date
/s/ Robert G. Johnson, Jr. Robert G. Johnson, Jr., M.D., Ph.D.	Chief Executive Officer (Principal Executive Officer)	March 30, 2006
/s/ David L. Johnson David L. Johnson	Principal Financial and Accounting Officer	March 30, 2006
/s/ Bruce Chabner Bruce Chabner, M.D.	Director	March 30, 2006

/s/ Peter Davis Peter Davis, Ph.D.	Director	March 30, 2006
/s/ Jean Deleage Jean Deleage, Ph.D.	Director	March 30, 2006
/s/ Charles Homcy Charles Homcy, M.D.	Director	March 30, 2006
/s/ Chaitan Khosla Chaitan Khosla, Ph.D.	Director	March 30, 2006
/s/ Christopher Walsh Christopher Walsh, Ph.D.	Director	March 30, 2006

INDEX TO EXHIBITS

Exhibit Number	Description
5.1	Opinion of Cooley Godward LLP.
23.1	Consent of Independent Registered Public Accounting Firm.
23.2	Consent of Cooley Godward LLP. Reference is made to Exhibit 5.1.
24.1	Power of Attorney (contained on the signature page).
99.1(1)	1996 Stock Option Plan, as amended.
99.2(1)	2000 Non-Employee Director Stock Option Plan.
99.3(1)	2000 Employee Stock Purchase Plan.

(1) Incorporated herein by reference to an exhibit to the Registrant’s Statement on Form S-1, as amended (No. 333-33732), declared effective on October 4, 2000.