Exhibit 3.1

CERTIFICATE OF AMENDMENT OF BYLAWS OF

PHARSIGHT CORPORATION

The undersigned, being duly elected, qualified, and acting Secretary of Pharsight Corporation (the “Company”) hereby certifies that the following amendments to the Company’s Bylaws were approved by the Board of Directors of the Company on October 18, 2007:

RESOLVED FURTHER: That Article VII, Section 34 of the Company’s Bylaws is hereby amended and restated to read as follows in its entirety:

Form and Execution of Certificates. The shares of the corporation shall be represented by certificates, provided that the Board of Directors may provide by resolution or resolutions that some or all of any or all classes or series of the corporation’s stock shall be uncertificated shares. Any such resolution shall not apply to shares represented by a certificate until such certificate is surrendered to the corporation. Every holder of stock in the corporation shall be entitled to have a certificate signed by, or in the name of the corporation by, the Chairman of the Board (if there be such an officer appointed), or by the President or any Vice President and by the Treasurer or Assistant Treasurer or the Secretary or Assistant Secretary, certifying the number of shares owned by him in the corporation. Any or all of the signatures on the certificate may be a facsimile. In case any officer, transfer agent, or registrar who has signed or whose facsimile signature has been placed upon a certificate shall have ceased to be such officer, transfer agent, or registrar before such certificate is issued, it may be issued with the same effect as if he were such officer, transfer agent, or registrar at the date of issue. Each certificate shall state upon the face or back thereof, in full or in summary, all of the powers, designations, preferences, and rights, and the limitations or restrictions of the shares authorized to be issued or shall, except as otherwise required by law, set forth on the face or back a statement that the corporation will furnish without charge to each stockholder who so requests the powers, designations, preferences and relative, participating, optional, or other special rights of each class of stock or series thereof and the qualifications, limitations or restrictions of such preferences and/or rights. Within a reasonable time after the issuance or transfer of uncertificated stock, the corporation shall send to the registered owner thereof a written notice containing the information required to be set forth or stated on certificates pursuant to this section or otherwise required by law or with respect to this section a statement that the corporation will furnish without charge to each stockholder who so requests the powers, designations, preferences and relative participating, optional or other special rights of each class of stock or series thereof and the qualifications, limitations or restrictions of such preferences and/or rights. Except as otherwise expressly provided by law, the rights and obligations of the holders of certificates representing stock of the same class and series shall be identical.

RESOLVED FURTHER: That Article VII, Section 36(a) of the Company’s Bylaws is hereby amended and restated to read as follows in its entirety:

(a) Transfers of record of shares of stock of the corporation shall be made only upon its books by the holders thereof, in person or by attorney duly authorized, and, if such stock is certificated, upon the surrender of a certificate or certificates for a like number of shares, properly endorsed.

IN WITNESS WHEREOF, the undersigned has hereunto set his hand and affixed the corporate seal this 22 day of October, 2007.

/s/ William Frederick

William Frederick

Secretary