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): April 17, 2003 MKS Instruments, Inc. (Exact name of registrant as specified in charter) Massachusetts 0-23621 04-2277512 (State or other juris- (Commission (IRS Employer diction of incorporation) File Number) Identification No.) Six Shattuck Road, Andover, Massachusetts 01810 (Address of principal executive offices) (Zip Code) Registrant's telephone number, including area code: (978) 975-2350 (Former name or former address, if changed since last report) ITEM 9. REGULATION FD DISCLOSURE (INFORMATION FURNISHED PURSUANT TO ITEM 12, "DISCLOSURE OF RESULTS OF OPERATIONS AND FINANCIAL CONDITION"). On April 17, 2003, MKS Instruments, Inc. announced its financial results for the quarter ended March 31, 2003. The full text of the press release issued in connection with the announcement is attached as Exhibit 99.1 to this Current Report on Form 8-K. In accordance with the procedural guidance in SEC Release No. 33-8216, the information in this Form 8-K and the Exhibit attached hereto is being furnished under "Item 9. Regulation FD Disclosure" rather than under "Item 12. Disclosure of Results of Operations and Financial Condition." The information shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934 (the "Exchange Act") or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933 or the Exchange Act, except as expressly set forth by specific reference in such a filing. 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. Date: April 17, 2003 MKS Instruments, Inc. By: /s/ Ronald C. Weigner ---------------------------------------- Ronald C. Weigner, Vice President & Chief Financial Officer EXHIBIT INDEX Exhibit No. Description 99.1 Press release dated April 17, 2003