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                                                                   EXHIBIT 10.51
                              EMPLOYMENT AGREEMENT

         THIS EMPLOYMENT AGREEMENT (the "Agreement") is made as of April 2, 2003
(the "Effective Date") by and between Gen-Probe Incorporated, a Delaware
corporation with offices at 10210 Genetic Center Drive, San Diego, California
92121 ("Gen-Probe"), and Henry L. Nordhoff (the "Executive").

         WHEREAS, on June 17, 1994, Gen-Probe and Executive entered into an
Employment Agreement specifying certain terms and conditions for Executive's
employment;

         WHEREAS, Executive is currently employed as an officer of Gen-Probe;

         WHEREAS, from the time the June 17, 1994 employment agreement was
signed until September 15, 2002, Gen-Probe was a wholly-owned subsidiary of
Chugai Pharmaceutical Co., Ltd.;

         WHEREAS, Chugai distributed its Gen-Probe shareholdings to its
shareholders in a "spin off" transaction on September 15, 2002;

         WHEREAS, the Board of Directors of Gen-Probe (the "Board"), having
considered the proposed spin-off transaction and other circumstances, deems it
in the best interest of Gen-Probe to offer this Agreement to the Executive and
the Executive desires to enter into this Agreement.

         ACCORDINGLY, the parties hereto agree as follows:

1.       TERM OF EMPLOYMENT. This Agreement shall be immediately effective. This
         Agreement, and Executive's employment hereunder, shall be for an
         indefinite term. At any time during the term of this Agreement, either
         party may terminate this Agreement, and Executive's employment, in
         accordance with the provision of Sections 6 and 7 of this Agreement.

2.       POSITION AND DUTIES. The Executive shall serve as President and Chief
         Executive Officer of Gen-Probe, and shall have commensurate
         responsibilities and authority. The Board of Directors may from time to
         time particularly specify the Executive's duties and authority. The
         Executive shall not engage in or perform duties for any other persons
         or entities that interfere with the performance of his duties
         hereunder, provided that the Executive may continue to serve on the
         boards of directors and boards of trustees on which he served on the
         Effective Date. Any outside board of director positions accepted by the
         Executive after the Effective Date will be subject to approval by the
         Board of Directors of Gen-Probe.

3.       SALARY, BONUS AND BENEFITS.

         (a)      SALARY. During the period of the Executive's employment,
                  Gen-Probe shall pay him an annual base salary at the rate the
                  Executive is being paid as of the Effective Date. This base
                  salary may be increased annually by the Board, subject to the
                  terms of this Agreement and consistent with the Executive's
                  performance

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                  and Gen-Probe's policy regarding adjustments in officer
                  compensation established from time to time by the Board. The
                  base salary shall not be decreased during the term of this
                  Agreement.

         (b)      BONUS. In addition, at the Board's discretion, the Executive
                  will be awarded incentive compensation, in the form of a cash
                  bonus for each fiscal year during his employment, based upon
                  performance. Executive's target bonus shall be seventy-five
                  percent (75%) of his base salary; however, the actual bonus
                  shall be set at the discretion of the Board.

         (c)      STOCK OPTIONS/RESTRICTED STOCK. In addition, not later than
                  June 30 during each year of the term on this Agreement, the
                  Executive will be awarded not less than 10,000 restricted
                  shares and not less than 50,000 options of Gen-Probe common
                  stock, if such options or restricted shares are then available
                  under an equity participation plan adopted by Gen-Probe. The
                  exercise price of any options granted hereunder shall be equal
                  to the last reported trade of Gen-Probe's common stock at the
                  close on the trading day preceding the effective date of the
                  grant. Options and restricted stock to be granted hereunder
                  shall fully vest within four (4) years of grant. The Board may
                  reasonably and in good faith adjust the minimum number of
                  shares or options to be granted hereunder if the Board
                  determines reasonably and in good faith that such an
                  adjustment is reasonable in light of any dividend or other
                  distribution, recapitalization, reclassification, stock split,
                  reverse stock split, reorganization, merger, consolidation,
                  split-up, spin-off, combination, repurchase, liquidation,
                  dissolution, or sale, transfer, exchange or other disposition
                  of all or substantially all of the assets of Gen-Probe, or
                  exchange of common stock or other securities of Gen-Probe,
                  issuance of warrants or other rights to purchase Common Stock
                  or other securities of Gen-Probe, or other similar corporate
                  transaction or event,

         (d)      LIFE INSURANCE. Gen-Probe will obtain and pay for a term life
                  insurance policy providing for payment of $1,000,000 in
                  benefits to the Executive's designated beneficiaries should
                  the Executive die during the term of this Agreement. (This
                  policy shall be in addition to any coverage provide by
                  Gen-Probe's group life insurance plan pursuant to subsection
                  (f), below.)

         (e)      DISABILITY INSURANCE. Gen-Probe will obtain and pay for a
                  long-term disability insurance policy providing for payment at
                  a rate of no less than $200,000 per annum to Executive should
                  Executive suffer a long-term disability during the term of
                  this Agreement. (This policy shall be in addition to any
                  coverage provide by Gen-Probe's group disability insurance
                  plan pursuant to subsection (f), below.)

         (f)      AD& D INSURANCE. Gen-Probe will obtain and pay for an AD&D
                  insurance policy providing for a benefit to Executive (or his
                  beneficiaries) of $400,000 (airplane) or $200,000 (automobile
                  or walking) should Executive suffer accidental death or
                  accidental disability during the term of this Agreement.

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         (g)      CLUBS. During the term of this Agreement, Gen-Probe will pay
                  Executive's annual dues for a membership in the Union League
                  Club of New York City. During the term of this Agreement,
                  Gen-Probe will also pay Executive's dues for a membership in
                  the Fairbanks Ranch Country Club. Upon termination of this
                  Agreement, Executive shall have own all right, title and
                  interest in the memberships in the Union League Club and
                  Fairbanks Ranch Country Club, free of any claim by Gen-Probe.
                  Executive shall be solely responsible for any continuing dues
                  or similar obligations after termination.

         (h)      OTHER BENEFITS. The Executive shall be entitled to participate
                  in the employee benefit programs (including but not limited to
                  medical, dental, life and disability insurance, 401K
                  retirement plan, and vacation program), as adopted and
                  maintained by Gen-Probe. Gen-Probe shall reimburse the
                  Executive for reasonable attorney's fees incurred in
                  connection with this Agreement, in an amount not in excess of
                  $6,000. The Executive may receive such other and additional
                  benefits as the Board may determine from time to time in its
                  sole discretion.

4.       EXPENSE REIMBURSEMENT. The Executive shall be entitled to receive
         prompt reimbursement for all reasonable and customary expenses incurred
         by him in performing services hereunder, including all expenses of
         travel and living expenses while away from home on business or at the
         request of, and in the service of Gen-Probe; provided, that such
         expenses are incurred and accounted for in accordance with the policies
         and procedures established by Gen-Probe.

5.       INDEMNIFICATION. Gen-Probe shall indemnify the Executive to the maximum
         extent permitted by law, by the by-laws of Gen-Probe and by the
         Indemnification Agreement dated August 19, 2002, between the Executive
         and Gen-Probe, as it may be amended (the "Indemnification Agreement"),
         if the Executive is made a party, or threatened to be made a party, to
         any threatened or pending legal action, suit or proceeding, whether
         civil, criminal, administrative or investigative, by reason of the fact
         that the Executive is or was an officer, director or employee of
         Gen-Probe or any subsidiary or affiliate thereof, in which capacity the
         Executive is or was serving at Gen-Probe's request, against reasonable
         expenses (including reasonable attorneys' fees), judgments, fines and
         settlement payments incurred by him in connection with such action,
         suit or proceeding.

6.       TERMINATION. The Executive may terminate his employment hereunder at
         any time, with or without Good Reason (as defined below) upon written
         notice to Gen-Probe. If Executive contends that Good Reason exists for
         his termination, such notice shall specifically and expressly state the
         grounds which he contends constitute Good Reason. Gen-Probe may
         terminate the Executive's employment hereunder at any time, subject to
         the terms of this Agreement, with or without Cause (as defined below)
         upon written notice to the Executive. If this Agreement is terminated,
         all compensation and benefits other than severance benefits described
         in Section 7 below, to the extent applicable, shall immediately cease,
         except that the Executive will be entitled, through the date of
         termination, to payment of his salary and benefits under Gen-Probe
         benefit programs and plans in accordance with their terms.

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         As used in this Agreement, "Good Reason" shall mean any of the
         following events that are not consented to by the Executive: (i) the
         removal of the Executive from his position as the Chief Executive
         Officer of Gen-Probe; (ii) a substantial and material diminution in the
         Executive's duties and responsibilities hereunder; (iii) a reduction of
         the Executive's base salary or target bonus percentage; (iv) the
         location of the Executive's assignment on behalf of Gen-Probe is moved
         to a location more than 30 miles from its present location; (v) the
         failure of Gen-Probe to obtain a satisfactory agreement from any
         successor to Gen-Probe to assume and agree to perform this Agreement;
         or (vi) a material breach by Gen-Probe of its obligations under this
         Agreement after notice in writing from the Executive and a reasonable
         opportunity for Gen-Probe to cure or substantially mitigate any
         material adverse effect of such breach. The Executive's consent to any
         event which would otherwise constitute Good Reason shall be
         conclusively presumed if the Executive does not exercise his rights to
         terminate this Agreement for Good Reason under this section within six
         (6) months of notice of the event.

         As used in this Agreement, "Cause" shall mean any of the following
         events: (i) any act of gross or willful misconduct, fraud,
         misappropriation, dishonesty, embezzlement or similar conduct on the
         part of Executive; (ii) the Executive's conviction of a felony or any
         crime involving moral turpitude (which conviction, due to the passage
         of time or otherwise, is not subject to further appeal); (iii) the
         Executive's misuse or abuse of alcohol, drugs or controlled substances
         and failure to seek and comply with appropriate treatment; (iv) willful
         and continued failure by the Executive to substantially perform his
         duties under this Agreement (other than any failure resulting from
         disability or from termination by the Executive for Good Reason) as
         determined by a majority of the Board after written demand from the
         Board of Directors for substantial performance is delivered to the
         Executive, and the Executive fails to resume substantial performance of
         his duties on a continuous basis within 30 days of such notice; (v) the
         death of the Executive; or (vi) the Executive becoming disabled such
         that he is not able to perform his usual duties for Gen-Probe for a
         period in excess of six (6) consecutive calendar months.

7.       SEVERANCE BENEFITS IN CERTAIN EVENTS. If Gen-Probe terminates the
         Executive's employment for reasons other than Cause, or if the
         Executive terminates his employment for Good Reason, the Executive
         shall be entitled to receive the following severance benefits:

         (a)      SALARY. The Executive shall continue to receive his base
                  salary, at the rate in effect at the time of his termination
                  of employment, in monthly installments commencing the first
                  day of the first month following termination and continuing
                  for an aggregate period of twenty-four (24) months (the
                  "Salary Continuation Period"); provided, however, that if
                  termination under this Section 7 occurs in connection with a
                  Change in Control, then the Executive shall receive a single
                  lump sum payment, payable within 10 days of termination, equal
                  to thirty-six (36) months' base salary.

                  For purposes of this Agreement, "Change in Control" shall have
                  the meaning set forth on Attachment "1" to this Agreement
                  (hereby incorporated by reference). For purposes of this
                  Agreement, a termination shall be "in connection with" a

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                  Change in Control if termination occurs within the period six
                  (6) months prior to or eighteen (18) months after a Change in
                  Control.

         (b)      BONUS. The Executive shall be entitled to receive a pro rata
                  portion of the bonus provided in Section 3(b) for the year in
                  which his employment terminates. The Executive shall also be
                  entitled to receive, in addition to the salary payment
                  described in Section 7(a), above, an amount equal to two times
                  the Executive's targeted level bonus in the year of the
                  termination; provided, however, that if termination under this
                  Section 7 occurs in connection with a Change in Control, then
                  the Executive shall be entitled to receive an amount equal to
                  three times the Executive's targeted level bonus in the year
                  of the termination. The amount payable hereunder shall be paid
                  in the same manner as and on the same schedule as the salary
                  compensation paid under subsection (a) above.

         (c)      HEALTH CARE AND LIFE INSURANCE COVERAGE. Continued health care
                  coverage under Gen-Probe's medical plan will be provided,
                  without charge, to the Executive and his eligible dependents
                  until the earlier of (i) Executive's sixty-fifth (65th)
                  birthday or (ii) the first date that the Executive is covered
                  under another employer's health benefit program providing
                  substantially the same or better benefit options to the
                  Executive without exclusion for any pre-existing medical
                  condition. The period of time medical coverage continues under
                  this Agreement will be counted as coverage time under COBRA.
                  Such coverage may be provided at Gen-Probe's option either by
                  payment directly to Gen-Probe's health insurance carrier,
                  through Gen-Probe's own employee medical expense plan if
                  Gen-Probe is self-insured, or through reimbursement of
                  Executive's COBRA premiums upon submission of reasonable
                  substantiation. As to life insurance, Gen-Probe will pay the
                  premium for continued life insurance coverage, if any, that
                  the Executive may have elected under Gen-Probe's Life
                  Insurance and Supplemental Life Insurance plan, subject to
                  payment by the Executive of the portion of such premium not
                  contributed by Gen-Probe under such plan, during the Salary
                  Continuation Period. After Executive reaches age 65, Gen-Probe
                  will provide for up to $10,000.00 per year in medical
                  reimbursement to cover medical or prescription expenses
                  incurred but not covered by either Medicare Part A and B or
                  Medicare Supplemental Insurance mentioned in the following
                  sentence. The Executive is expected to carry Supplemental
                  Medicare Insurance and to comply with the Insurance Plan
                  restrictions to maximize coverage.

         (d)      401(k) PLAN. The Executive's interest in any unvested
                  contributions made by Gen-Probe to the Executive's 401(k)
                  account shall vest as of the date of termination.

         (e)      OUTPLACEMENT SERVICES. Gen-Probe agrees to provide Executive
                  with outplacement services during the first six months of the
                  Salary Continuation Period at a level not lower than the
                  services provided to senior officers of Gen-Probe prior to the
                  Effective Date.

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         (f)      TAX MATTERS. All compensation described in this Agreement will
                  be subject to Gen-Probe's collection of all applicable
                  federal, state and local income and employment withholding
                  taxes.

         (g)      RELEASE OF CLAIMS. Gen-Probe's obligation to make the payments
                  and provide the benefits hereunder shall be conditioned upon
                  Executive's execution of a release of all claims that he then
                  may have other than claims under Section 5 or the
                  Indemnification Agreement, in standard form and content. The
                  release shall be mutual and shall also be signed on behalf of
                  Gen-Probe.

8.       EXCISE TAX ON PARACHUTE PAYMENTS.

         (a)      GROSS-UP PAYMENT. If it is determined that any payment or
                  distribution of any type to the Executive or for his benefit
                  by Gen-Probe, any of its affiliates, any person who acquires
                  ownership or effective control of Gen-Probe or ownership of a
                  substantial portion of Gen-Probe's assets (within the meaning
                  of section 280G of the Internal Revenue Code of 1986, as
                  amended (the "Code"), and the regulations thereunder) or any
                  affiliate of such person, whether paid or payable or
                  distributed or distributable pursuant to the terms of this
                  Agreement or otherwise (the "Total Payments"), would be
                  subject to the excise tax imposed by section 4999 of the Code
                  or any interest or penalties with respect to such excise tax
                  (such excise tax and any such interest or penalties are
                  collectively referred to as the "Excise Tax"), then the
                  Executive shall be entitled to receive an additional payment
                  (a "Gross-Up Payment") in an amount calculated to ensure that
                  after the Executive pays all taxes (and any interest or
                  penalties imposed with respect to such taxes), including any
                  Excise Tax, imposed upon the Gross-Up Payment, the Executive
                  retains an amount of the Gross-Up Payment equal to the Excise
                  Tax imposed upon the Total Payments.

         (b)      DETERMINATION BY ACCOUNTANT. All determinations and
                  calculations required to be made under this Section 8 shall be
                  made by an independent accounting firm selected by Gen-Probe
                  from among the largest four (4) accounting firms in the United
                  States (the "Accounting Firm"). The Accounting Firm shall
                  provide its determination (the "Determination"), together with
                  detailed supporting calculations regarding the amount of any
                  Gross-Up Payment and any other relevant matter, to the
                  Executive and Gen-Probe within five (5) days after the
                  Executive or Gen-Probe made a request (if the Executive
                  reasonably believes that any of the Total Payments may be
                  subject to the Excise Tax). If the Accounting Firm determines
                  that no Excise Tax is payable by the Executive, it shall
                  furnish the Executive with a written statement that it has
                  concluded that no Excise Tax is payable (including the reasons
                  therefor) and that the Executive has substantial authority not
                  to report any Excise Tax on his federal income tax return. If
                  a Gross-Up Payment is determined to be payable, it shall be
                  paid to the Executive within five (5) days after the
                  Determination has been delivered to him or Gen-Probe. Any
                  determination by the Accounting Firm shall be binding upon
                  Gen-Probe and the Executive, absent manifest error.

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         (c)      OVER- AND UNDERPAYMENTS. As a result of uncertainty in the
                  application of section 4999 of the Code at the time of the
                  initial determination by the Accounting Firm hereunder, it is
                  possible that Gross-Up Payments not made by Gen-Probe should
                  have been made ("Underpayment") or that Gross-Up Payments will
                  have been made by Gen-Probe that should not have been made
                  ("Overpayment"). In either event, the Accounting Firm shall
                  determine the amount of the Underpayment or Overpayment that
                  has occurred. In the case of an Underpayment, Gen-Probe shall
                  promptly pay the amount of such Underpayment to the Executive
                  or for his benefit. In the case of an Overpayment, the
                  Executive shall, at the direction and expense of Gen-Probe,
                  take such steps as are reasonably necessary (including the
                  filing of returns and claims for refund), follow reasonable
                  instructions from, and procedures established by, Gen-Probe,
                  and otherwise reasonably cooperate with Gen-Probe to correct
                  such Overpayment, provided, however, that (i) the Executive
                  shall in no event be obligated to return to Gen-Probe an
                  amount greater than the net after-tax portion of the
                  Overpayment that the Executive has retained or has recovered
                  as a refund from the applicable taxing authorities and (ii)
                  this provision shall be interpreted in a manner consistent
                  with the intent of Subsection (a) above, which is to make the
                  Executive whole, on an after-tax basis, from the application
                  of the Excise Tax, it being understood that the correction of
                  an Overpayment may result in the Executive's repaying to
                  Gen-Probe an amount that is less than the Overpayment.

         (d)      LIMITATION ON PARACHUTE PAYMENTS. Any other provision of this
                  Section 8 notwithstanding, if the Excise Tax could be avoided
                  by reducing the Total Payments by $10,000 or less, then the
                  Total Payments shall be reduced to the extent necessary to
                  avoid the Excise Tax and no Gross-Up Payment shall be made. If
                  the Accounting Firm determines that the Total Payments are to
                  be reduced under the preceding sentence, then Gen-Probe shall
                  promptly give the Executive notice to that effect and a copy
                  of the detailed calculation thereof. The Executive may then
                  elect, in his sole discretion, which and how much of the Total
                  Payments are to be eliminated or reduced (as long as after
                  such election no Excise Tax shall be payable), and the
                  Executive shall advise Gen-Probe in writing of his election
                  within ten (10) days of receipt of notice. If the Executive
                  make no such election within such ten (10)-day period, then
                  Gen-Probe may elect which and how much of the Total Payments
                  are to be eliminated or reduced (as long as after such
                  election no Excise Tax shall be payable), and it shall notify
                  the Executive promptly of such election.

9.       MISCELLANEOUS.

         (a)      ARBITRATION. Executive and Gen-Probe agree that any and all
                  claims or disputes that in any way relate to or arise out of
                  Executive's employment with Gen-Probe or the termination of
                  such employment (including but not limited to claims under
                  this Agreement or any other contract, tort claims, and
                  statutory claims of employment discrimination, retaliation or
                  harassment) shall be resolved exclusively through final and
                  binding arbitration in San Diego, California. Executive and
                  Gen-Probe waive any rights to a jury trial in connection with
                  such

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                  claims or disputes. The costs of the arbitration, including
                  the fees of the arbitrator, shall be borne exclusively by
                  Gen-Probe. Any such arbitration shall take place in San Diego,
                  California and shall be conducted by a single neutral
                  arbitrator who shall be a retired federal or state judge, to
                  be appointed by Judicial Arbitration and Mediation Services
                  ("JAMS") in accordance with JAMS rules. The applicable
                  procedural rules of JAMS shall govern the arbitration. The
                  arbitrator's decision shall be delivered in writing and shall
                  disclose the essential findings and conclusion on which the
                  arbitrator's decision is based. The parties shall be permitted
                  to conduct adequate discovery to allow for a full and fair
                  exploration of the issues in dispute in the arbitration
                  proceeding. The arbitrator may grant any relief which
                  otherwise would have been available to the parties in a court
                  proceeding. The decision and award of the arbitrator shall be
                  final and binding, and judgment upon the arbitrator's award
                  may be entered by any court of competent jurisdiction.

         (b)      GOVERNING LAW. This Agreement shall be construed and enforced
                  in accordance with and be governed by the laws of the State of
                  California.

         (c)      ENTIRE AGREEMENT. This Agreement and the Indemnification
                  Agreement set forth the entire agreement and understanding
                  between the Executive and Gen-Probe on the subject matter
                  hereof, and supersede any other negotiations, agreements,
                  understandings, oral agreements, representations and past or
                  future practices, whether written or oral, on the subject
                  matter hereof. No provision of this Agreement may be amended,
                  supplemented, modified, cancelled, or discharged unless such
                  amendment, supplement, modification, cancellation or discharge
                  is agreed to, in writing, signed by the Executive and a duly
                  authorized officer of Gen-Probe (other than the Executive);
                  and no provisions hereof may be waived, except in writing, so
                  signed by or on behalf of the party granting such waiver.

         (d)      VALIDITY. The invalidity or unenforceability of any provision
                  or provisions of this Agreement shall not affect the validity
                  or enforceability of any other provision of this Agreement,
                  which shall remain in full force and effect.

         (e)      NOTICES. For the purposes of this Agreement, notices, demands
                  and all other communications provided for in this Agreement
                  shall be in writing and shall be deemed to have duly given
                  when personally delivered or mailed by United States certified
                  or registered mail, return receipt requested, postage prepaid,
                  addressed as follows:

                  If to the Executive:

                           Henry L. Nordhoff

                  If to Gen-Probe:

                           Vice President, Administration

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                           Gen-Probe Incorporated
                           10210 Genetic Center Drive
                           San Diego, California 92121

                  With a copy to:

                           General Counsel
                           Gen-Probe Incorporated
                           10210 Genetic Center Drive
                           San Diego, California 92121

         (f)      SUCCESSORS. Gen-Probe will require any successor (whether
                  direct or indirect, by purchase, merger, consolidation or
                  otherwise) to all or substantially all the business and/or
                  assets of Gen-Probe, by agreement in form and substance
                  satisfactory to the Executive, expressly to assume and agree
                  to perform this Agreement in the same manner and to the same
                  extent that Gen-Probe would be required to perform it if no
                  such succession had taken place. This Agreement and all rights
                  under the Agreement shall be binding upon and shall inure to
                  the benefit of and be enforceable by the party's personal or
                  legal representatives, executors, administrators, heirs, and
                  successors.

         (g)      NO RIGHT TO CONTINUED EMPLOYMENT. Nothing herein shall be
                  construed as giving the Executive any rights to continued
                  employment with Gen-Probe, and Gen-Probe shall continue to
                  have the right to terminate the Executive's employment at any
                  time, with or without cause, subject to the provisions of this
                  Agreement.

         In witness whereof, the parties have executed this Agreement.

Executive:                                  Gen-Probe Incorporated:

/s/ Henry L. Nordhoff                              /s/ Robin L. Vedova
----------------------------                By -------------------------------
Henry L. Nordhoff                                      Robin L. Vedova
                                                Vice President, Administration

                                                   /s/ R. William Bowen
                                            By -------------------------------
                                                       R. William Bowen
                                              Vice President and General Counsel

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                                 ATTACHMENT "1"

                        DEFINITION OF "CHANGE IN CONTROL"

         Change in Control.

"Change in Control" shall mean a change in ownership or control of Gen-Probe
effected through any of the following transactions:

         (a)      any person or related group of persons (other than Gen-Probe
or a person that, prior to such transaction, directly or indirectly controls, is
controlled by, or is under common control with, Gen-Probe) directly or
indirectly acquires beneficial ownership (within the meaning of Rule 13d-3 under
the Exchange Act) of securities possessing more than fifty percent (50%) of the
total combined voting power of Gen-Probe's outstanding securities by means of
any transaction or series of transactions; or

         (b)      there is a change in the composition of the Board over a
period of thirty-six (36) consecutive months (or less) such that a majority of
the Board members (rounded up to the nearest whole number) ceases, by reason of
one or more proxy contests for the election of Board members, to be comprised of
individuals who either (i) have been Board members continuously since the
beginning of such period or (ii) have been elected or nominated for election as
Board members during such period by at least a majority of the Board members
described in clause (i) who were still in office at the time such election or
nomination was approved by the Board; or

         (c)      the stockholders of Gen-Probe approve a merger or
consolidation of Gen-Probe with any other corporation (or other entity), other
than a merger or consolidation which would result in the voting securities of
Gen-Probe outstanding immediately prior thereto continuing to represent (either
by remaining outstanding or by being converted into voting securities of the
surviving entity or another entity) more than 66-2/3% of the combined voting
power of the voting securities of Gen-Probe or such surviving entity outstanding
immediately after such merger or consolidation; provided, however, that a merger
or consolidation effected to implement a recapitalization of Gen-Probe (or
similar transaction) in which no person acquires more than 25% of the combined
voting power of Gen-Probe's then outstanding voting securities shall not
constitute a Change in Control; or

         (d)      the stockholders of Gen-Probe ap-prove a plan of complete
liquidation of Gen-Probe or an agreement for the sale or disposition by
Gen-Probe of all or substantially all of Gen-Probe's assets.