Exhibit 99.1

Stock Symbol: PH – NYSE

PARKER’S FISCAL Q2 NET INCOME UP 49 PERCENT; CASH FLOW REMAINS STRONG

Cleveland, Ohio: January 20, 2004 – Parker Hannifin Corporation (NYSE: PH) today reported a 49-percent increase in fiscal second-quarter net income to $55.8 million, or 47 cents per diluted share, on sales of $1.62 billion for the period ended December 31, 2003. For the same period last year, the company reported quarterly net income of $37.6 million, or 32 cents per diluted share on sales of $1.52 billion.

“This quarter’s results come from improved volume, combined with solid operating performance as we see the benefits from our strategic financial performance initiatives,” said Parker CEO Don Washkewicz. “All of the company’s operating segments recorded year-over-year margin improvement except Aerospace, which still achieved a double-digit operating margin.”

Leading the gain was the North American Industrial segment, which improved operating margin to 7.5 percent on a five percent increase in sales. The company noted improved strength in construction, heavy-duty truck and semiconductor markets. International Industrial units increased sales 18.1 percent (attributed mostly to currency rate changes) and operating margin was 6.7 percent.

In the company’s Climate & Industrial Controls segment (previously included in the “Other” segment), second-quarter sales were relatively flat while operating margin increased to 7.2 percent.

In Aerospace, sales were 1.2 percent lower and operating margin was 11.3 percent.

In the “Other” segment, comprised of Wynn Specialty Chemicals and Astron metal buildings, sales were 11.4 percent higher than the prior year second quarter (mostly the result of currency rate changes) and operating margin improved to 7.0 percent.

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Year-to-Date Results

For the first six months of fiscal 2004, the company recorded net income of $112.5 million, or 95 cents per diluted share on sales of $3.21 billion. Net income is up 14.1 percent over last year’s $98.5 million, or 84 cents per diluted share on sales of $3.10 billion.

The company again noted strong cash flow from operations of $378.2 million, or 12 percent of sales, and will continue to look for growth opportunities, as evidenced by its recent tender offer for shares of Denison International plc, which is expected to close in the third fiscal quarter.

“Acquisitions are still an important part of our accelerated growth plan,” said Washkewicz. “We’re very excited about Denison’s solid, profitable performance in Europe and significant presence in Asia, especially in China. We look forward to adding the Denison product line to Parker’s and expanding our total systems capabilities.”

Outlook

For the second half of fiscal-year 2004, the company said it expects sales in the Industrial and Other segments to increase modestly, with continued profitability improvements. Sales and margins are expected to be down slightly in the Climate & Industrial Controls segment. In Aerospace, the company said sales should stabilize, but it did not expect near-term margins to improve without a corresponding improvement in aftermarket volume.

“While we are pleased to see some improvement in this quarter’s operating performance and in recent order trends, we remain hopeful market conditions will continue to improve,” said Washkewicz. “Our balance sheet is getting healthier and we’re staying focused on our Win Strategy to drive growth, profitability and cash flow.”

NOTICE OF CONFERENCE CALL: Parker Hannifin’s conference call and slide presentation to discuss its fiscal second-quarter results is available to all interested parties via live webcast today at 10:00 a.m. ET, on the company’s investor information web site, www.phstock.com. To access the call, click on the “Live Webcast” link. From this link, users also may complete a pre-call system test and register for e-mail notification of future events and information available from Parker. The call will be archived on the site for two weeks.

With annual sales exceeding $6 billion, Parker Hannifin is the world’s leading diversified manufacturer of motion and control technologies and systems, providing precision-engineered solutions for a wide variety of commercial, mobile, industrial and aerospace markets. The company employs more than 46,000 people in 44 countries around the world. For more information, visit the company’s web site at www.parker.com, or its investor information site at www.phstock.com.

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Forward-looking statements contained in this and other written and oral reports are made based on known events and circumstances at the time of release, and as such, are subject in the future to unforeseen uncertainties and risks. All statements regarding future performance, earnings projections, events or developments are forward-looking statements. It is possible that the future performance and earnings projections of the company and individual segments may differ materially from current expectations, depending on economic conditions within both its industrial and aerospace markets, and the company’s ability to achieve anticipated benefits associated with announced realignment activities, strategic initiatives to improve operating margins, and growth initiatives. A change in economic conditions in individual markets may have a particularly volatile effect on segment results. Among the other factors which may affect future performance are: changes in business relationships with and purchases by or from major customers or suppliers, including delays or cancellations in shipments; uncertainties surrounding timing, successful completion or integration of acquisitions; threats associated with and efforts to combat terrorism; competitive market conditions and resulting effects on sales and pricing; increases in raw-material costs that cannot be recovered in product pricing; and global economic factors, including currency exchange rates, difficulties entering new markets and general economic conditions such as interest rates. The company makes these statements as of the date of this disclosure, and undertakes no obligation to update them.

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PARKER HANNIFIN CORPORATION—DECEMBER 31, 2003

CONSOLIDATED STATEMENT OF INCOME

Note: Certain prior period amounts have been reclassified to conform to the current year presentation.

CONSOLIDATED BALANCE SHEET