Costco Wholesale Corporation Reports December Sales Results.

ISSAQUAH, Wash. -- Costco Wholesale Corporation (Nasdaq: COST) today reported net sales of $6.37 billion for the five weeks ended January 1, 2006, an increase of 10 percent from $5.77 billion in the same five-week period of the prior fiscal year. For the first eighteen weeks of its fiscal year ended January 1, 2006, the Company reported net sales of $20.22 billion, an increase of 11 percent from $18.17 billion during the similar 18-week period of the prior fiscal year.

Comparable sales for the 5-week and 18-week periods ended January 1, 2006, were as follows:

5 Weeks        18 Weeks
                 ------------  --------------
US                    6%              8%
International         8%              9%

Total Company         7%              8%
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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# 3893301). This recorded message will be available today through 5:00 p.m. (PT) on Friday, January 6, 2006.

Costco currently operates 471 warehouses, including 346 in the United States and Puerto Rico, 66 in Canada, 17 in the United Kingdom, five in Korea, four in Taiwan, five in Japan and 28 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 20 to 22 new warehouses, including the relocation of two warehouses to larger and better-located facilities, prior to the end of its 53-week 2006 fiscal year ending on September 3, 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.