Amendment to the Employment Agreement



 Exhibit 10(d) 
 AMENDMENT TO THE EMPLOYMENT AGREEMENT BETWEEN 
 SIGMA-ALDRICH CORPORATION AND JAI NAGARKATTI 

 WHEREAS, the Sigma-Aldrich Corporation (“Company”) and Jai Nagarkatti (“Chief Executive Officer”) previously entered
into an employment agreement (“Agreement”) effective as of January 1, 2006; and 
 WHEREAS, the Company and Chief Executive
Officer retained the right to amend the Agreement in Section 3.10 thereof; 
 WHEREAS, the Plan has been administered in good faith
compliance with Section 409A of the Internal Revenue Code of 1986, as amended, and the regulations and other guidance promulgated thereunder (“Code Section 409A”); and 
 WHEREAS, the Company and Chief Executive Officer desire to amend the Agreement, effective December 31, 2008, to reflect documentary compliance with
Code Section 409A. 
 NOW, THEREFORE, in consideration of the foregoing, the Company and Chief Executive Officer hereby agree to amend
the Agreement, effective December 31, 2008, as follows: 
 1. Section 1.1(i) is deleted in its entirety and replaced with the following: 

“(i) “Good Reason” when used with reference to a voluntary termination by Executive from his employment with Company, shall mean
(i) a material reduction in Executive’s base salary as in effect on the date hereof, or as the same may be increased from time to time, during the Employment Period; or (ii) a material reduction in the Executive’s authorities,
duties, or responsibilities during the Employment Period; or notice of termination.” 
 2. Section 2.4(c)(iii) is deleted in its entirety and
replaced with the following: 
 “(iii) In the event that the Executive is determined to be a specified employee in accordance with
Section 409A of the Internal Revenue Code of 1986, as amended, and the regulations and other guidance issued thereunder for purposes of any severance pay payment under this subsection (c), such severance payments shall begin on the first
payroll date that is more than six months following the date of separation from service, but only to the extent that such payments do not satisfy either the short term deferral exception to Code Section 409A described in 26 CFR
§1.409A-1(b)(4) (“Short Term Deferral Exception”) or to the extent such payments do not satisfy the Short Term Deferral Exception, the involuntary termination exception to Code Section 409A described in 26 CFR
§1.409A-1(b)(9). At all times, the right to all such installment payments made under this subsection (c) shall be treated as the right to a series of separate payments within the meaning of 26 CFR §1.409A-2(b)(2)(iii).”

 3. The last sentence of Section 2.4(d) is deleted in its entirety and replaced with the following: 
 “Good Reason will only exist if the Executive provides the Company with written notice of Good Reason within a period not to exceed 90 days after the
initial existence of the condition alleged to give rise to Good Reason, the Company fails to remedy the condition within 30 days of such notice, 








 
and such Good Reason termination is within two years following the initial existence of one or more conditions giving rise to Good Reason. In the event that
the Executive is determined to be a specified employee in accordance with Section 409A of the Internal Revenue Code of 1986, as amended, and the regulations and other guidance issued thereunder for purposes of any severance pay payment under
this subsection (c), such severance payments shall begin on the first payroll date that is more than six months following the date of separation from service, but only to the extent that such payments do not satisfy either the short term deferral
exception to Code Section 409A described in 26 CFR §1.409A-1(b)(4) (“Short Term Deferral Exception”) or to the extent such payments do not satisfy the Short Term Deferral Exception, the involuntary termination exception to Code
Section 409A described in 26 CFR §1.409A-1(b)(9). At all times, the right to all such installment payments made under this subsection (d) shall be treated as the right to a series of separate payments within the meaning of 26 CFR
§1.409A-2(b)(2)(iii).” 
 IN WITNESS WHEREOF, the parties hereto have executed this Amendment to the Agreement this 30th day of
December, 2008. 
  

			
	SIGMA-ALDRICH CORPORATION
		
	By:	 	 /s/ Richard A. Keffer

	Name:	 	Richard A. Keffer
	Title:	 	Secretary
	
	Chief Executive Officer
	
	 /s/ Jai Nagarkatti

	Jai Nagarkatti