SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d) OF

THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): May 3, 2011

SIGMA-ALDRICH CORPORATION

(Exact Name of Registrant as Specified in its Charter)

Registrant’s telephone number, including area code: (314) 771-5765

N/A

(Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

Item 5.03.

At the annual meeting of shareholders of Sigma-Aldrich Corporation (“the Company”) held on May 3, 2011 (the “2011 Annual Meeting”), the shareholders approved two amendments to the Company’s Certificate of Incorporation (the “Amendments”). The text of the Amendments and the description of such Amendments on pages 58-59 under the caption “Amendments to Article Eleventh and Article Twelfth of the Certificate of Incorporation, as Amended” in the Proxy Statement of Sigma-Aldrich Corporation dated March 14, 2011 (the “Proxy Statement”), are filed as Exhibits 99.1, 99.2 and 99.3, respectively, and incorporated by reference herein. A copy of the Company’s Certificate of Incorporation and all amendments is filed as Exhibit 3(a) hereto.

Item 5.07. Submission of Matters to a Vote of Security Holders

As indicated above, on May 3, 2011, the Company held the Annual Meeting. Of the 121,801,532 shares outstanding and entitled to vote, 107,541,310 shares were represented at the meetings, or an 88.29% quorum. The final results for each of the matters submitted to a vote of shareholders at the Annual Meeting are as follows:

Item No. 1:

All of the board’s nominees for director were elected to serve until the Company’s 2012 Annual Meeting or until their respective successors are elected and qualified by the shareholders, by the votes set forth in the table below:

Item No. 2:

The material terms of the performance criteria for the Company’s performance-based awards under the Amended and Restated 2003 Long-Term Incentive Plan were approved by the shareholders, by the votes set forth in the table below

Item No. 3:

The appointment of KPMG LLP as the Company’s independent registered public accountant for the fiscal year ending December 31, 2011 was ratified by the shareholders by the votes set forth in the table below:

Item No. 4:

The amendment to Article Eleventh of the Certificate of Incorporation, as amended, as described in the Proxy Statement was approved by the shareholders by the vote set forth in the table below:

Item No. 5:

The amendment to Article Twelfth of the Certificate of Incorporation, as amended, as described in the Proxy Statement was approved by the shareholders by the vote set forth in the table below:

Item No. 6:

The approval on a non-binding advisory basis, of the Company’s named executive officer compensation, as disclosed in the Proxy Statement by the vote set forth in the table below:

Item No. 7:

The determination of the frequency of future advisory votes on executive compensation (every one, two or three years) received the non-binding advisory votes set forth in the table below:

The Board of Directors will take into account these results in determining the frequency it shall call for an advisory vote on executive compensation.

Item 9.01 Financial Statements and Exhibits

(d) Exhibits. See Exhibit Index.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Dated: May 6, 2011

EXHIBIT INDEX