ISSAQUAH, WA -- (MARKET WIRE) -- 10/05/2006 -- Costco Wholesale Corporation ("Costco") (NASDAQ: COST) today reported net sales of $5.56 billion for the month of September, the five weeks ended October 1, 2006, an increase of 8% from $5.14 billion in the same five-week period last year. Comparable sales increased 4% during this five-week period (3% domestically and 12% internationally).

Costco currently operates 488 warehouses, including 359 in the United States and Puerto Rico, 68 in Canada, 18 in the United Kingdom, five in Korea, four in Taiwan, five in Japan and 29 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 an additional 15 to 16 new warehouses prior to the end of calendar year 2006.

As previously announced, the Company plans to release its fourth quarter and fiscal year 2006 operating results on Thursday, October 12, 2006. A conference call to discuss these results is scheduled for 8:00 a.m (PT) on October 12, and will be available via a webcast on www.costco.com (click on Investor Relations and "Webcasts").

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 #2328173). This recorded message will be available today through 5:00 p.m. (PT) on Friday, October 6, 2006.

Certain statements contained in this document 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, conditions affecting the acquisition, development, ownership or use of real estate, actions of vendors, rising costs associated with employees (including health care and workers' compensation costs), rising costs associated with the acquisition of merchandise (including the direct and indirect effects of the rising cost of petroleum-based products and fuel and energy costs), geopolitical conditions and other risks identified from time to time in the Company's public statements and reports filed with the Securities and Exchange Commission.