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

Exhibit 99.1 [MKS LOGO] FOR IMMEDIATE RELEASE INVESTOR RELATIONS CONTACT: Ronald Weigner Vice President & Chief Financial Officer 978.975.2350 MKS INSTRUMENTS REPORTS FIRST QUARTER 2003 FINANCIAL RESULTS Andover, Mass. -- April 17, 2003 -- MKS Instruments, Inc. (NASDAQ: MKSI), a leading worldwide provider of products that measure, control, power and monitor critical parameters of semiconductor and other advanced manufacturing process environments, today reported first quarter 2003 financial results. First quarter 2003 revenues totaled $72.8 million, a 23 percent increase compared to first quarter 2002 revenues of $59.1 million and a 6 percent decrease from fourth quarter 2002 revenues of $77.6 million. The first quarter 2003 GAAP net loss was $7.4 million or $0.14 per share on 51.4 million basic shares outstanding compared to the first quarter 2002 GAAP net loss of $11.8 million or $0.25 per share on 46.3 million basic shares outstanding and the fourth quarter 2002 GAAP net loss of $19.2 million or $0.37 per share on 51.3 million basic shares outstanding. The fourth quarter 2002 GAAP net loss included a non-cash charge of $13.4 million or $0.26 per share for the reversal of MKS' net deferred tax assets. The first quarter 2003 pro forma net loss (defined as net income before amortization of acquired intangible assets, and other acquisition and disposition related charges, net of income taxes) was $3.7 million or $0.07 per share. The first quarter 2002 pro forma net loss was $4.3 million or $0.09 per share. The fourth quarter 2002 pro forma net loss was $16.9 million or $0.33 per share, and excluding the non-cash deferred tax charge, the loss was $3.5 million or $0.07 per share.

Since 1999, MKS has reported financial results on a pro forma basis as a complement to results provided in accordance with accounting principles generally accepted in the United States. MKS' management uses such pro forma measures internally to evaluate the company's performance and manage its operations, and believes that pro forma measures provide useful information for understanding operating results and comparing prior periods. John R. Bertucci, Chairman, Chief Executive Officer and President of MKS, said, "In the first quarter, we continued to make inroads in high-growth semiconductor applications and to penetrate other markets. Our margins improved as we began to realize the benefit of previously announced cost reduction initiatives, including manufacturing consolidation and tightened expense control. Our balance sheet continued to remain strong with cash and investments of approximately $142 million." Mr. Bertucci continued, "Looking forward, second quarter 2003 revenues could range from $73 to $78 million. This sales range, combined with anticipated reduced costs associated with up to 10 mandatory days off, could result in a second quarter 2003 GAAP net loss of $0.10 to $0.15 per share. Excluding amortization of acquired intangible assets, which the Company currently estimates would be $3.8 million, the pro forma net loss could range from $0.03 to $0.08 per share." "We remain positive about our long-term growth prospects," Mr. Bertucci added. "We believe that our breadth of technology and depth of application expertise differentiates MKS, and we continue to implement strategies to increase our opportunities for growth in the next upturn."

Management will host a conference call on Thursday, April 17, 2003 at 5:00 p.m. (EDT) to discuss these financial results. To listen to this call, dial 800-218-4007 (domestic) or 303-262-2075 (international), or access the live call and a rebroadcast at www.mksinstruments.com. To hear a replay through April 24, 2003, dial 303-590-3000, passcode 531834#. MKS Instruments, Inc. is a leading worldwide provider of instruments, components and subsystems that measure, control, power and monitor critical parameters of semiconductor and other advanced manufacturing process environments. MKS' products are used to manufacture semiconductors, optical filters, flat panel displays, magnetic and optical storage media, medical imaging equipment, architectural glass, solar panels and gas lasers. This release contains projections or other forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 regarding MKS' future growth and the future financial performance of MKS. These projections or statements are only predictions. Actual events or results may differ materially from those in the projections or other forward-looking statements set forth herein. Among the important factors that could cause actual events to differ materially from those in the projections or other forward-looking statements are the fluctuations in capital spending in the semiconductor industry, fluctuations in net sales to MKS' major customers, potential fluctuations in quarterly results, the failure of MKS and acquired companies to realize the anticipated benefits of their combined businesses, the challenges and risks involved with integrating the operations of MKS and acquired companies, dependence on new product development, rapid technological and market change, acquisition strategy, manufacturing and sourcing risks, volatility of stock price, international operations, financial risk management, and future growth subject to risks. Readers are referred to MKS' filings with the Securities and Exchange Commission, including its most recent Annual Report on Form 10-K, for a discussion of these and other important risk factors concerning MKS and its operations. MKS is under no obligation to, and expressly disclaims any obligation to, update or alter its forward-looking statements, whether as a result of new information, future events or otherwise. ###

MKS INSTRUMENTS, INC. UNAUDITED CONSOLIDATED STATEMENTS OF INCOME (IN THOUSANDS, EXCEPT PER SHARE DATA) Three Months Ended March 31, ----------------------- 2003 2002 -------- -------- Net sales $ 72,777 $ 59,067 Cost of sales 47,371 39,847 -------- -------- Gross profit 25,406 19,220 Research and development 11,232 9,132 Selling, general and administrative 17,819 17,058 Amortization of acquired intangible assets 3,778 2,205 Purchase of in-process technology - 6,100 -------- -------- Loss from operations (7,423) (15,275) Interest income, net 280 426 -------- -------- Loss before income taxes (7,143) (14,849) Provision (benefit) for income taxes (See NOTE 1 below) 287 (3,062) -------- -------- Net loss $ (7,430) $(11,787) ======== ======== Net loss per share (See NOTE 2 below) $ (0.14) $ (0.25) ======== ======== Weighted average shares outstanding 51,380 46,288 The following supplemental pro forma earnings information is presented to aid in understanding the MKS operating results: Supplemental Pro Forma Earnings Information Net loss $ (7,430) $(11,787) Adjustments: Amortization of acquired intangible assets 3,778 2,205 Purchase of in-process technology - 6,100 Tax effect of adjustments (See NOTE 1 below) - (772) -------- -------- Pro forma net loss before amortization of acquired intangible assets, and other acquisition and disposition related charges, net of income taxes $ (3,652) $ (4,254) ======== ======== Pro forma net loss per share before amortization of acquired intangible assets, and other acquisition and disposition related charges, net of income taxes $ (0.07) $ (0.09) ======== ======== Weighted average shares outstanding 51,380 46,288 NOTE 1: MKS recorded a tax benefit of $3,062 for the three months ended March 31, 2002. In the three months ended December 31, 2002, MKS recorded a full valuation allowance against its net deferred tax assets. Accordingly, MKS has not recorded a deferred tax benefit from the net operating loss incurred in the quarter ended March 31, 2003. The provision for income taxes of $287 includes tax expense from foreign operations and state taxes. NOTE 2: Due to the net loss for the quarter, net loss per share is based on the basic number of weighted average shares outstanding.

MKS INSTRUMENTS, INC. UNAUDITED CONSOLIDATED BALANCE SHEETS (IN THOUSANDS) March 31, December 31, 2003 2002 -------- ----------- ASSETS Cash and short-term investments $123,085 $128,714 Trade accounts receivable 49,499 45,505 Inventories 72,423 73,235 Other current assets 5,039 6,098 -------- -------- Total current assets 250,046 253,552 Property, plant and equipment, net 80,734 82,595 Long-term investments 19,000 15,980 Goodwill 259,719 259,781 Other acquired intangible assets 63,943 67,720 Other assets 5,931 5,995 -------- -------- Total assets $679,373 $685,623 ======== ======== LIABILITIES AND STOCKHOLDERS' EQUITY Short-term debt $ 17,957 $ 18,472 Accounts payable 17,323 15,301 Other accrued expenses 27,141 27,771 -------- -------- Total current liabilities 62,421 61,544 Long-term debt 11,307 11,726 Other long-term liabilities 1,621 1,663 Stockholders' equity: Common stock 113 113 Additional paid-in capital 579,265 579,175 Retained earnings 21,193 28,623 Other stockholders' equity 3,453 2,779 -------- -------- Total stockholders' equity 604,024 610,690 -------- -------- Total liabilities and stockholders' equity $679,373 $685,623 ======== ========