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                                                                   Exhibit 10.14

                                 PROMISSORY NOTE

$22,750.00                                                 Palo Alto, California
                                                                   June 15, 1999

      FOR VALUE RECEIVED, the undersigned hereby unconditionally promises to pay
to the order of PHARSIGHT CORPORATION, a California corporation (the "Company"),
at 800 West El Camino Real, Suite 200, Mountain View, CA 94040, or at such other
place as the holder hereof may designate in writing, in lawful money of the
United States of America and in immediately available funds, the principal sum
of twenty-two thousand seven hundred fifty Dollars ($22,750.00) together with
interest accrued from the date hereof on the unpaid principal at the rate of 6%
per annum, or the maximum rate permissible by law (which under the laws of the
State of California shall be deemed to be the laws relating to permissible rates
of interest on commercial loans), whichever is less, as follows:

Principal Repayment. The outstanding principal amount hereunder shall be due and
payable in full on May 1, 2003 (the "Principal Repayment Date"); and

Interest Payments. Interest shall be payable in arrears on the Principal
Repayment Date and shall be calculated on the basis of a 360-day year for the
actual number of days elapsed;

provided, however, that in the event that the undersigned's employment by or
association with the Company or its Affiliate is terminated for any reason prior
to payment in full of this Note, this Note shall be accelerated and all
remaining unpaid principal and interest shall become due and payable immediately
after such termination.

      If the undersigned fails to pay any of the principal and accrued interest
when due, the Company, at its sole option, shall have the right to accelerate
this Note, in which event the entire principal balance and all accrued interest
shall become immediately due and payable, and immediately collectible by the
Company pursuant to applicable law.

      This Note may be prepaid at any time without penalty. All money paid
toward the satisfaction of this Note shall be applied first to the payment of
interest as required hereunder and then to the retirement of the principal.

      The full amount of this Note is secured by a pledge of shares of Common
Stock of the Company, and is subject to all of the terms and provisions of the
Early Exercise Stock Purchase Agreement and Stock Pledge Agreement of even date
herewith between the undersigned and the Company.

      The undersigned hereby represents and agrees that the amounts due under
this Note are not consumer debt, and are not incurred primarily for personal,
family or household purposes, but are for business and commercial purposes only.
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      The undersigned hereby waives presentment, protest and notice of protest,
demand for payment, notice of dishonor and all other notices or demands in
connection with the delivery, acceptance, performance, default or endorsement of
this Note.

      The holder hereof shall be entitled to recover, and the undersigned agrees
to pay when incurred, all costs and expenses of collection of this Note,
including without limitation, reasonable attorneys' fees.

      This Note shall be governed by, and construed, enforced and interpreted in
accordance with, the laws of the State of California, excluding conflict of laws
principles that would cause the application of laws of any other jurisdiction.


                                    Signed            /s/ Robin Kehoe
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                                                        Robin Kehoe