Costco Wholesale Corporation Reports March Sales Results.

ISSAQUAH, Wash. -- Costco Wholesale Corporation (Nasdaq:COST) today reported net sales of $4.87 billion for the five weeks ended April 3, 2005, an increase of 10 percent from $4.41 billion in the same five-week period of the prior fiscal year.

For the first 31 weeks of its 2005 fiscal year ended April 3, 2005, the Company reported net sales of $30.49 billion, an increase of 10 percent from $27.79 billion during the similar 31-week period of the prior fiscal year.

Comparable sales for the 5-week and 31-week periods ended April 3, 2005, were as follows:

5 Weeks        31 Weeks
                         ------------   ------------
    US                        6%             6%
    International            13%            10%

    Total Company             7%             7%
                         ============   ============

This year's five-week period included 34 days of sales compared to 35 days last year, reflecting the timing of Easter. This calendar shift impacted sales negatively by approximately one to two percent.

Reported net sales were reduced by the implementation of Emerging Issues Task Force Issue No. 03-10 ("EITF 03-10"), "Application of Issue No. 02-16 by Resellers to Sales Incentives Offered to Consumers by Manufacturers," which was effective at the beginning of the Company's fiscal 2004 third quarter, February 16, 2004. Sales for the 5-week reporting periods are on a comparable after-coupon basis; however, had sales for the 31-week year-to-date period last year been reported under EITF 03-10, the total Company reported net sales increase would have been 10 percent and the total Company comparable sales increase would have been 8 percent.

Additional discussion of these sales results is available on a pre-recorded telephone message. You can access the recording by dialing 1-800-642-1687 (conference ID# 5075979). This recorded message will be available today through 5:00 PM (PDT) on Friday, April 8, 2005.

Costco currently operates 452 warehouses, including 334 in the United States and Puerto Rico, 64 in Canada, 15 in the United Kingdom, five in Korea, four in Taiwan, five in Japan and 25 in Mexico. The Company also operates Costco Online, an electronic commerce web site, at www.costco.com and at www.costco.ca in Canada. The Company plans to open 9 to 11 additional new warehouses prior to the end of its fiscal year 2005, on August 28, 2005.

Certain statements contained in this release constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. For these purposes, forward-looking statements are statements that address activities, events, conditions or developments that the Company expects, or anticipates, may occur in the future. Such forward-looking statements involve risks and uncertainties that may cause actual events, results or performance to differ materially from those indicated by such statements. These risks and uncertainties include, but are not limited to, domestic and international economic conditions, including exchange rates, the effects of competition and regulation, consumer and small business spending patterns and debt levels, rising costs associated with employees (including health care and workers' compensation costs), conditions affecting the acquisition, development, ownership or use of real estate, actions of vendors, and other risks identified from time to time in the Company's public statements and reports filed with the SEC.