Document:

<PAGE>

                                                                    Exhibit 4.18

                                   QIAGEN N.V.
                                CHANGE IN CONTROL
                                    AGREEMENT

     This Agreement is entered into as of the 30th day of September, 2002 by and
between QIAGEN N.V., a corporation organized under the laws of the Netherlands
(the "Company") and Peer Michael Schatz (the "Executive").

     WHEREAS the Executive is the Managing Director of the Company and has been
employed in such capacity since 1996;

     WHEREAS because of the skills and experience of the Executive and his
knowledge of the Company, his service to the Company is very important to the
future success of the Company;

     WHEREAS the Executive desires to enter into this Agreement to provide him
with certain financial protection in the event of a change in control of the
Company; and

     WHEREAS the Board of Directors of the Company has determined that it is in
the best interests of the Company to enter into this Agreement.

     NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the Company and the Executive
agree as follows:

1.   Change in Control Defined. As used herein, a "Change in Control" shall be
deemed to have occurred if (i) there is a sale or transfer of all or
substantially all of the assets of the Company in one or a series of
transactions; or (ii) there is a merger or consolidation of the Company whether
or not approved by the Board of Directors, other than a merger or consolidation
which would result in the voting securities of the Company outstanding
immediately prior thereto continuing to represent (either by remaining
outstanding or by being converted into voting securities of the surviving entity
or the parent of such corporation) more than 50% of the total voting power
represented by the voting securities of the Company or such surviving entity or
parent of such corporation outstanding immediately after such merger or
consolidation.

2.   Vesting on a Change in Control. Upon the effective date of a Change in
Control, all options to purchase common shares of the Company held by Executive
as of such date and granted to the Executive after execution of this Agreement)
shall be immediately 100% fully vested and shall be otherwise exercisable in
accordance with the terms of the stock option agreement, pursuant to which they
were granted.

3.   Compensation. In the event that there is a Change in Control, the Company
shall pay to the Executive a single payment equal to (a) five times the
Executive's annual salary during the preceding one-year period, including the
year of such termination, plus (b) 100% of the Executive's annual bonus as
agreed prior to the Change of Control.

4.   No Duplication of Compensation or Benefits. The Executive's compensation
set forth in Sections 2 and 3 above shall replace, and be provided in lieu of,
any severance compensation and benefits that may be provided to Executive under
any other agreement with the exception of approved agreements with subsidiaries
of QIAGEN N.V.; provided, that this prohibition against duplication shall not be
construed to otherwise limit Executive's rights as to payments or benefits

<PAGE>

provided under any pension plan, deferred compensation, stock, stock option or
similar plan sponsored by the Company; and further provided, that
notwithstanding the foregoing, all other rights and obligations set forth in
Executive's Employment Agreement shall continue as provided for therein.

5.   Enforceability; Reduction. If any provision of this Agreement shall be
deemed invalid or unenforceable as written, this Agreement shall be construed,
to the greatest extent possible, or modified, to the extent allowable by law, in
a manner which shall render it valid and enforceable and any limitation on the
scope or duration of any provision necessary to make it valid and enforceable
shall be deemed to be a part thereof. No invalidity or unenforceability of any
provision contained herein shall affect any other portion of this Agreement.

6.   Entire Agreement. This Agreement embodies the entire agreement and
understanding between the parties hereto with respect to the subject matter
hereof and supersedes all prior oral or written agreements and understandings
relating to the specific subject matter hereof. No statement, representation,
warranty, covenant or agreement of any kind not expressly set forth in this
Agreement shall affect, or be used to interpret, change or restrict, the express
terms and provisions of this Agreement.

7.   Modifications and Amendments. The terms and provisions of this Agreement
may be modified or amended only by written agreement executed by all parties
hereto.

8.   Assignment. The rights and obligations under this Agreement may not be
assigned by either party hereto without the prior written consent of the other
party.

9.   Benefit. All statements, representations, warranties, covenants and
agreements in this Agreement shall be binding on the parties hereto and shall
inure to the benefit of the respective successors and permitted assigns of each
party hereto. Nothing in this Agreement shall be construed to create any rights
or obligations except among the parties hereto, and no person or entity shall be
regarded as a third-party beneficiary of this Agreement.

10.  Governing Law. This Agreement and the rights and obligations of the parties
hereunder shall be construed in accordance with and governed by the law of the
Netherlands, without giving effect to the conflict of law principles thereof.

     IN WITNESS WHEREOF, the parties have executed this Agreement as of the day
and year first above written.

                                       COMPANY:

                                       QIAGEN N.V.

                                       By: /s/ Prof. Dr. Detlev H. Riesner
                                           ----------------------------------
                                       Prof. Dr. Detlev H. Riesner
                                       Chairman of the Supervisory Board

                                       EXECUTIVE:

                                       /s/ Peer M. Schatz
                                       --------------------------------------
                                       Peer M. Schatz
                                       Chief Executive Officer

                                      -2-<PAGE>

                                                                    Exhibit 4.19

To Metin Colpan

Dear Dr. Metin Colpan:

In addition to your contract as a managing director with the Company dated July
1, 1985, we hereby agree as follows:

    1.  In the event of a "change of control" you will receive compensation. A
        "change of control" is defined as
           -   As used herein, a "Change in Control" shall be deemed to have
               occurred if (i) there is a sale or transfer of all or
               substantially all of the assets of the Company in one or a series
               of transactions; or (ii) there is a merger or consolidation of
               the Company whether or not approved by the Board of Directors,
               other than a merger or consolidation which would result in the
               voting securities of the Company outstanding immediately prior
               thereto continuing to represent (either by remaining outstanding
               or by being converted into voting securities of the surviving
               entity or the parent of such corporation) more than 50% of the
               total voting power represented by the voting securities of the
               Company or such surviving entity or parent of such corporation
               outstanding immediately after such merger or consolidation.

    2.  The compensation is calculated as follows:
               ((13 x the then current monthly salary)+bonus) x 5 = compensation

           -   the monthly salary is the agreed gross salary as per the
               employment contract in the month in which the change of control
               occurs
           -   the bonus is the gross bonus and other variable cash components
               that were agreed for the year in which the change of control
               occurs
           -   Other compensation components (e.g. company car) are not
               considered for the calculation of the compensation
           -   The treatment of granted stock options is agreed on in a separate
               document.

    3.  The compensation is a gross sum which is subject to tax and other
        standard deductions

    4.  The compensation is to be paid within 3 months after the change of
        control

    5.  This agreement is valid for all changes of control pursuant to article 1
        of this agreement and which occurs on or before Oct. 10, 2007.

    QIAGEN GmbH

    (Represented by the sole shareholder, QIAGEN NV)<PAGE>

                                                                    Exhibit 4.20

To Peer M. Schatz

Dear Peer M. Schatz:

In addition to your contract as a managing director with the Company dated May
1, 1993, we hereby agree as follows:

    1.  In the event of a "change of control" you will receive compensation. A
        "change of control" is defined as

           -   As used herein, a "Change in Control" shall be deemed to have
               occurred if (i) there is a sale or transfer of all or
               substantially all of the assets of the Company in one or a series
               of transactions; or (ii) there is a merger or consolidation of
               the Company whether or not approved by the Board of Directors,
               other than a merger or consolidation which would result in the
               voting securities of the Company outstanding immediately prior
               thereto continuing to represent (either by remaining outstanding
               or by being converted into voting securities of the surviving
               entity or the parent of such corporation) more than 50% of the
               total voting power represented by the voting securities of the
               Company or such surviving entity or parent of such corporation
               outstanding immediately after such merger or consolidation.

    2.  The compensation is calculated as follows:
               ((13 x the then current monthly salary)+bonus) x 5 = compensation

           -   the monthly salary is the agreed gross salary as per the
               employment contract in the month in which the change of control
               occurs
           -   the bonus is the gross bonus and other variable cash components
               that were agreed for the year in which the change of control
               occurs
           -   Other compensation components (e.g. company car) are not
               considered for the calculation of the compensation
           -   The treatment of granted stock options is agreed on in a separate
               document.

    3.  The compensation is a gross sum which is subject to tax and other
        standard deductions

    4.  The compensation is to be paid within 3 months after the change of
        control

    5.  This agreement is valid for all changes of control pursuant to article 1
        of this agreement and which occurs on or before Oct. 10, 2007.

    QIAGEN GmbH

    (Represented by the sole shareholder, QIAGEN NV)

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00049-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00049-of-00352.parquet"}], [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00049-of-00352.parquet"}]]