Exhibit 4.20



Roland Sackers



[Private Address]



| | Re: | Employment Agreement
| | --- | --------------------



Dear Roland:



This letter is to
confirm our understanding with respect to your employment in the United States by QIAGEN N.V., QIAGEN GmbH, and QIAGEN North American Holding (collectively, the Company) for the period of calendar year 2004. In consideration of the
mutual promises and covenants contained in this Agreement, and for other good and valuable consideration, the receipt and sufficiency of which are hereby mutually acknowledged, we have agreed as follows:



1. Employment.



(a) Subject to the terms and conditions of this Agreement, the Company will employ you, and you will be
employed by the Company and/or any Company Affiliate designated by the Company, initially as CFO and VP Finance of QIAGEN N.V. and QIAGEN GmbH and VP Finance of QIAGEN North American Holding, reporting to the CEO of QIAGEN N.V. You will have the
responsibilities, duty and authority commensurate with those positions, including, without limitation:



| |  |  | Managing all activities related to a CFO, including but not limited to financial and management accounting, reporting, taxes, financing and financial markets;
| | - |  | --------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | Setting up and integrating a QIAGEN North America Administration Company in Germantown including mainly all accounting, management accounting, human resources and IT activities in
North America;
| | - |  | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | Integrating QIAGEN North America Administration Company into the philosophy of the QIAGEN Group with regard to vision;
| | - |  | ----------------------------------------------------------------------------------------------------------------------



| |  |  | Integrating QIAGEN North America Administration Company into the philosophy of the QIAGEN North America companies with regards to the service level to be performed by this Company.
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



You will also perform such other and/or
different services for the Company as may be assigned to you from time to time by the Board or the CEO. The principal location at which you will perform such services initially will be the Companys facility located at Germantown, Maryland,
although you will be available to perform services at any other Company facility and to travel as the needs of business may require.



(b) Devotion to Duties. While you are employed hereunder, you will use your best efforts, skills and abilities to perform
faithfully all duties assigned to you pursuant to this Agreement and will devote your full business time and energies to the business and affairs of the Company. While you are employed hereunder, you will not undertake any other employment from any
person or entity without the prior written consent of the Company.





---

(c) Ability To Work In United States.You are responsible for ensuring that
all documentation required for you to work in the United States is obtained and that all passports and travel documents are valid while living away from your home country. QIAGEN North American Holding will reimburse reasonable fees and travel
expenses associated with obtaining these documents.



2. Term of
Employment In The United States.



(a) Your
employment hereunder runs for the term of January 1, 2004 through December 31, 2004 (the Term) unless renewed in writing for up to six (6) months by the mutual agreement of the parties hereto. Upon conclusion of this Agreement, provided
that your employment with QIAGEN GmbH in Germany and QIAGEN N.V. in the Netherlands has not otherwise been terminated, you will continue to be employed in those countries under the terms of your separate employment agreements with those entities
relating to your employment in those countries.



(b) Notwithstanding the foregoing, your employment hereunder may terminate prior to December 31, 2004 upon the first to occur of the following:



(i) Immediately upon your death;



(ii) By the Company:



(A) By written notice to you effective the date of such notice, for Cause (as defined below); or



(B) By written notice to you effective the
date of such notice and subject to Section 4 hereof, without Cause; or



(iii) By you at any time by written notice to the Company effective ninety (90) days after the date of such notice; or



(c) Definition of Cause. For purposes of this Agreement, Cause shall be defined as set forth under the
common law of Maryland and shall include (i) your conviction of a felony, either in connection with the performance of your obligations to the Company or which otherwise materially and adversely affects your ability to perform such obligations, (ii)
your willful disloyalty or deliberate dishonesty, (iii) the commission by you of an act of fraud or embezzlement against the Company, or (iv) a material breach by you of any material provision of this Agreement which breach is not cured within 30
days after delivery to you by the Company of written notice of such breach, provided that if such breach is not capable of being cured within such 30 day period, you will have a reasonable additional period to cure such breach but only if you
promptly commence and continue good faith efforts to cure such breach.



3.
Compensation/Living Expenses/Benefits.



(a) Base Salary. During the Term, North American Holding will pay you a base salary at the annual rate of USD 164,000 (the Base Salary). If there is a 10% difference either way to the exchange rate Euro  US Dollar
(Basis EURO/USD 1.15 compared to average of the monthly exchange rate of QIAGENs finance department), then this compensation shall be adjusted accordingly. The Base Salary will be payable in substantially equal installments in accordance with
the payroll practices of the entity paying. The Company will deduct from each such installment all



2



---

amounts required to be deducted or withheld under applicable law or under any employee benefit plan in which you participate. However, you will remain liable
for the payment of any income taxes due based on this or any other income received from the Company.



(b) Annual Bonus. In addition to the Base Salary, the Company may pay you a discretionary performance bonus (Annual
Bonus) of up to 25% of your annual Base Salary.



(c) Living Expenses. Because you will be living away from your place of residence while working in the United States, QIAGEN North American Holding will pay you a per-diem allowance of USD 50 each day you are
physically present in the US for meal and incidental expenses and a per-diem allowance of USD 150 each day you are physically present in the US for lodging expenses. You must maintain adequate records regarding your expenses (e.g. account book,
statement of expenses, trip sheets, receipts, paid bills etc.). The per-diems will be based upon the rules under Internal Revenue Code section 274 and related regulations and notices/pronouncements as amended. The US companys method of paying
per-diems will govern the operation of the expenses.



(d) Automobile/Other Amenities. QIAGEN North American Holding will also place at your disposal, free of charge, a medium-class vehicle (e.g. Lexus RX 330, BMW 5er) for business and private use. Should there be any additional need
(e.g. the need to acquire electrical appliances in the US), QIAGEN North American Holding will reimburse you for those expenditures as well, within any reasonable amounts, and only upon proper documentation.



(e) Home Leave. During the Term you will be entitled
to one (1) home flight between Düsseldorf/Köln and Washington D.C. (max total amount: EUR 4.000). In the event of an emergency situation (defined as the death or life-threatening accident or illness of an immediate member of the family
such as father, mother, life companion, children), an additional home leave will be granted. In addition, during the Term your family will be entitled to two (2) home flights between Düsseldorf/Köln and Washington D.C.(max total amount:
EUR 8.000 each). In the event of an emergency situation (defined as the death or life-threatening accident or illness of an immediate member of the family such as father, mother, life companion, children), an additional home leave will be granted.



(f) Vacation and Holidays. You will
receive paid holidays in accordance with QIAGEN North American Holdings policies. In addition, you will continue to be eligible to accrue and use the vacation set forth in your employment agreement with QIAGEN GmbH and QIAGEN N.V. All vacation
days will be taken at times mutually agreed by you and the Company and will be subject to the business needs of the Company.



(g) Sick Leave. You will be eligible to continue to receive your Base Salary for up to six (6) weeks in the event of your own
personal illness.



(h) Income Tax
Preparation. QIAGEN North American Holding will procure the services of a tax consulting firm at the companys expense in order to assist you with the preparation and filing of your German and your US income tax returns (max amount of EURO
10.000). Independent of QIAGENs information or the assistance of the tax-consulting firm, you will be responsible for the timely filing and compilation of all necessary tax records and relevant documents. As well, you are responsible for your
personal taxes, especially regarding other incomes than your salary package. To the extent required, you must provide copies of US tax payment certificates in the US to the HR department in Hilden, in order to prove the respective tax exemption
situation to the tax administration.



3



---

(i) Other Fringe Benefits. You will not be eligible to participate in the benefit
plans offered to the Companys U.S. employees. Your participation in benefits offered through QIAGEN GmbH pursuant to your employment in Germany will continue during the Term. You should thoroughly review your personal insurance policies for
life, accident, travel and household goods in order to determine whether or not you might need any additional insurance protection. QIAGEN will conclude a supplementary health insurance at QIAGEN North American Holdings expense for you and
your family. Should an emergency situation arise (defined as a life-threatening accident or life-threatening illness that requires lengthy hospitalization) QIAGEN North American Holding will reimburse such costs to a reasonable extent in accordance
with the supplementary health insurance. QIAGEN GmbH will pay 50 % as before of any German health insurance if necessary.



(j) Reimbursement of Expenses. Upon presentation of documentation of such expenses reasonably satisfactory to the Company, the
Company will reimburse you for all ordinary and reasonable out-of-pocket business expenses (including travel expenses) that are reasonably incurred by you in furtherance of the Companys business in accordance with the Companys policies
with respect thereto as in effect from time to time.



(k) Relocation. QIAGEN North American Holding will pay for the cost of shipping, storing and insuring of your household goods to the USA during the Term up to EURO 1.000.



4. Compensation Upon Termination. In the event of the termination of your employment hereunder for any reason or for no reason prior
to the end of the Term, upon submission of proper documentation, QIAGEN North American Holding will reimburse you  to a reasonable extent  the expenses incurred for your own and your family return flights as well as any relocation of
personal belongings from Washington DC to Cologne. In addition, QIAGEN North American Holding will compensate you as follows.



(a) Definition of Accrued Obligations. For purposes of this Agreement, Accrued Obligations means (i) the portion of
your Base Salary as has accrued prior to any termination of your employment with the Company and has not yet been paid, (ii) an amount equal to the value of your accrued unused vacation days, (iii) the amount of any Annual Bonus earned and accrued
but not yet paid, which amount will include a pro rata portion of any Annual Bonus which would have been earned if such termination had not occurred, and (iv) the amount of expenses properly incurred by you on behalf of the Company prior to any such
termination and not yet reimbursed.



(b)
Termination for Cause, upon Death, By You Voluntarily or As a Result of The Expiration of the Term on December 31, 2004. If your employment hereunder is terminated either (i) by the Company for Cause, (ii) as a result of your death, (iii) by
you voluntarily or (iv) as a result of the expiration of the Term on December 31, 2004, QIAGEN North American Holding will pay the Accrued Obligations to you promptly following such termination and shall have no further obligations hereunder.



(c) Termination Without Cause. If your
employment hereunder is terminated by the Company without Cause:



(i) QIAGEN North American Holding will pay the Accrued Obligations to you promptly following such termination.



4



---

(ii) QIAGEN North American Holding will pay you an amount equal to the two (2) times your
annual Base Salary plus two (2) times your full Annual Bonus.



5. Payments
Upon a Change in Control.



(a) 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 QIAGEN N.V. in one or a series of transactions; or (ii) there is
a merger or consolidation of QIAGEN N.V. 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.



(b) Compensation. In the event that there is a Change in Control, QIAGEN North American Holding shall pay you a single payment
equal to (a) two (2) times your Base Salary pursuant to this Agreement plus (b) two (2) times your full Annual Bonus pursuant to this Agreement.



(c) No Duplication of Compensation or Benefits. The compensation set forth in Section 5(b) above shall be in addition to any
compensation paid to you by QIAGEN N.V. pursuant to your Change in Control Agreement executed effective September 30, 2002 and any compensation paid to you by QIAGEN GmbH pursuant to your Change in Control Agreement with that entity . With those
limited exceptions, the compensation set forth in Section 5(b) shall replace, and be provided in lieu of, any severance compensation and benefits that may be provided to you under any other agreement with QIAGEN N.V., QIAGEN GmbH or QIAGEN North
American Holding, provided, that this prohibition against duplication shall not be construed to otherwise limit your rights as to payments or benefits 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 this Agreement shall continue as provided for herein.



6. Prohibited Competition.



(a) For a period of 1 year after the termination of the
employment contract, you may not, without the Companys prior written consent, engage in any activities that in any way whatsoever directly or indirectly compete with the Company in the nucleic acid handling separation and/or purification
industry or a company affiliated with it, and you may not establish, conduct (alone or with others) or cause the conduct of any competing business or take any interest in or be employed in any way whatsoever by such business, whether or not for
consideration.



(b) If you violate the
non-competition clause contained in this Agreement, you will forfeit to the Company a penalty equal to 1/12 of your annual Base Salary for each month that you are in breach, payable on demand.



(c) Upon each breach of the non-competition clause contained
in this Article, the period referred to in Section 6(a) will be extended by the duration of that breach.



5



---

7. Confidentiality. Neither during the term of the employment contract nor upon termination thereof may you inform
any third party in any form, directly or indirectly, of any particulars concerning or related to the business conducted by the Company or its affiliated companies, which you could reasonably have known were not intended for third parties, regardless
of whether such information includes any reference to its confidential nature or ownership and regardless of how you learned of the particulars.



8. Survival of Acknowledgements and Agreements. Your acknowledgements and agreements set forth in Sections 6 and 7 will survive the termination of this Agreement
and the termination of your employment hereunder for any reason or for no reason.



9. Injunctive Relief. You hereby expressly acknowledge that any breach or threatened breach of any of the terms and/or conditions set forth in Sections 6 or 7 of this Agreement will result in substantial, continuing and irreparable
injury to the Company. Therefore, in addition to any other remedy that may be available to the Company, the Company will be entitled to injunctive or other equitable relief by a court of appropriate jurisdiction in the event of any breach or
threatened breach of the terms of Section 6 or 7 of this Agreement.



10.
Disclosure to Future Employers. You will provide, and the Company, in its discretion, may similarly provide, a copy of the covenants contained in Sections 5 and 6 of this Agreement to any business or enterprise which you may, directly or
indirectly, own, manage, operate, finance, join, control or in which you may participate in the ownership, management, operation, financing, or control, or with which you may be connected as an officer, director, employee, partner, principal, agent,
representative, consultant or otherwise.



11. Records. Upon termination
of your employment hereunder for any reason or for no reason and at any other time requested by the Company, you will deliver to the Company any property of the Company which may be in your possession, including products, materials, memoranda,
notes, records, reports, or other documents or photocopies of the same.



12.
Representations. You hereby represent and warrant to the Company that you understand this Agreement, that you enter into this Agreement voluntarily and that your employment under this Agreement will not conflict with any legal duty owed by
you to any other party, or with any agreement to which you are a party or by which you are bound, including, without limitation, any non-competition or non-solicitation provision contained in any such agreement. You will indemnify and hold harmless
the Company Group and its officers, directors, security holders, partners, members, employees, agents and representatives against loss, damage, liability or expense arising from any claim based upon circumstances alleged to be inconsistent with such
representation and warranty.



13. General.



(a) Notices. All notices, requests, consents and
other communications hereunder which are required to be provided, or which the sender elects to provide, in writing, will be addressed to the receiving partys address set forth above or to such other address as a party may designate by notice
hereunder, and will be either (i) delivered by hand, (ii) sent by overnight courier, or (iii) sent by registered or certified mail, return receipt requested, postage prepaid. All notices, requests, consents and other communications hereunder will be
deemed to have been given either (i) if by hand, at the time of the delivery thereof to the receiving party at the address of such party set forth above, (ii) if sent by overnight courier, on the next business day following the day such notice is
delivered to the courier service, or (iii) if sent by registered or certified mail, on the fifth business day following the day such mailing is made.



6



---

(b) Entire Agreement. This Agreement embodies the entire agreement and
understanding between the parties hereto with respect to your employment in the United States during the 2004 calendar year and supersedes all prior oral or written agreements and understandings relating to this subject matter. It does not supersede
any agreements to the extent they relate to your employment with QIAGEN N.V. or QIAGEN GmbH in the Netherlands or Germany. No statement, representation, warranty, covenant or agreement of any kind not expressly set forth in this Agreement will
affect, or be used to interpret, change or restrict, the express terms and provisions of this Agreement.



(c) Modifications and Amendments. The terms and provisions of this Agreement may be modified or amended only by written agreement
executed by the parties hereto.



(d)
Waivers and Consents. The terms and provisions of this Agreement may be waived, or consent for the departure therefrom granted, only by written document executed by the party entitled to the benefits of such terms or provisions. No such
waiver or consent will be deemed to be or will constitute a waiver or consent with respect to any other terms or provisions of this Agreement, whether or not similar. Each such waiver or consent will be effective only in the specific instance and
for the purpose for which it was given, and will not constitute a continuing waiver or consent.



(e) Assignment. The Company may assign its rights and obligations hereunder to any person or entity that succeeds to all or
substantially all of the Companys business or that aspect of the Companys business in which you are principally involved or to any Company Affiliate. You may not assign your rights and obligations under this Agreement without the prior
written consent of the Company and any such attempted assignment by you without the prior written consent of the Company will be void.



(f) Benefit. All statements, representations, warranties, covenants and agreements in this Agreement will be binding on the parties
hereto and will inure to the benefit of the respective successors and permitted assigns of each party hereto.



(g) Governing Law. This Agreement and the rights and obligations of the parties hereunder will be construed in accordance with and
governed by the law of Maryland, without giving effect to the conflict of law principles thereof.



(h) Jurisdiction, Venue and Service of Process. Any legal action or proceeding with respect to this Agreement will be brought in
the courts of Maryland or of the United States of America located in Maryland or Washington, D.C. By execution and delivery of this Agreement, each of the parties hereto accepts for itself and in respect of its property, generally and
unconditionally, the exclusive jurisdiction of the aforesaid courts.



(i) Severability. The parties intend this Agreement to be enforced as written. However, (i) if any portion or provision of this Agreement is to any extent declared illegal or unenforceable by a duly authorized
court having jurisdiction, then the remainder of this Agreement, or the application of such portion or provision in circumstances other than those as to which it is so declared illegal or unenforceable, will not be affected thereby, and each portion
and provision of this Agreement will be valid and enforceable to the fullest extent permitted by law, and (ii) if any provision, or part thereof, is held to be unenforceable because of the duration of such provision, the geographic area covered
thereby, or other aspect or scope of such provision, the court making such determination will have the power to reduce the duration, geographic area of such provision, or other



7



---

aspect or scope of such provision, and/or to delete specific words and phrases (blue-penciling), and in its reduced or blue-penciled form, such
provision will then be enforceable and will be enforced.



(j) Headings and Captions. The headings and captions of the various subdivisions of this Agreement are for convenience of reference only and will in no way modify or affect the meaning or construction of any of
the terms or provisions hereof.



(k) No
Waiver of Rights, Powers and Remedies. No failure or delay by a party hereto in exercising any right, power or remedy under this Agreement, and no course of dealing between the parties hereto, will operate as a waiver of any such right, power or
remedy of the party. No single or partial exercise of any right, power or remedy under this Agreement by a party hereto, nor any abandonment or discontinuance of steps to enforce any such right, power or remedy, will preclude such party from any
other or further exercise thereof or the exercise of any other right, power or remedy hereunder. The election of any remedy by a party hereto will not constitute a waiver of the right of such party to pursue other available remedies. No notice to or
demand on a party not expressly required under this Agreement will entitle the party receiving such notice or demand to any other or further notice or demand in similar or other circumstances or constitute a waiver of the rights of the party giving
such notice or demand to any other or further action in any circumstances without such notice or demand.



(l) Counterparts. This Agreement may be executed in two or more counterparts, and by different parties hereto on separate
counterparts, each of which will be deemed an original, but all of which together will constitute one and the same instrument.



(m) Opportunity to Review. You hereby acknowledge that you have had adequate opportunity to review these terms and conditions and
to reflect upon and consider the terms and conditions of this Agreement, and that you have had the opportunity to consult with counsel of your own choosing regarding such terms. You further acknowledge that you fully understand the terms of this
Agreement and have voluntarily executed this Agreement.



If the
foregoing accurately sets forth our agreement, please so indicate by signing and returning to us the enclosed copy of this Agreement.



Very truly yours,QIAGEN, N.V., QIAGEN GmbH, QIAGEN NORTH AMERICAN HOLDINGBy:

/s/ Peer M. SchatzName:

Peer M. SchatzTitle:

Managing DirectorBy:

/s/ Prof. Dr. D. RiesnerName:

Prof. Dr. D. RiesnerTitle:

Chairman of the Supervisory Board QIAGEN N.V.




Accepted and Approved



|                   |  |  |  |                
|------------------ |  |  |  | ---------------
|                   |  | 
|/s/ Roland Sackers |  |  |  | January 5, 2004
|Roland Sackers     |  |  |  | Date           



8