Exhibit 99.1

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COSTCO WHOLESALE CORPORATION REPORTS FIRST QUARTER

FISCAL YEAR 2012 OPERATING RESULTS

ISSAQUAH, Wash., December 8, 2011—Costco Wholesale Corporation (“Costco” or the “Company”) (Nasdaq: COST) announced today its operating results for the first quarter (twelve weeks) of fiscal 2012, ended November 20, 2011.

Net sales for the quarter increased thirteen percent to $21.18 billion from $18.82 billion during the first quarter of fiscal 2011. Comparable sales for the first quarter of fiscal 2012 were as follows:

Inflation in gasoline prices and strengthening foreign currencies had a positive impact on comparable sales. Excluding these effects, comparable sales for the twelve-week period were as follows:

Net income for the quarter was $320 million, or $.73 per diluted share, compared to $312 million, or $.71 per diluted share, for the first quarter of fiscal 2011. First quarter results were negatively impacted by a $24 million charge relating to the settlement of an income tax audit of the Company’s 50% owned Mexico joint venture. The impact on net income attributable to Costco was $12 million, or $.03 per diluted share. Also negatively impacting this year’s results was a $17 million charge, or $.04 per diluted share, for contributions to the Yes on 1183 Coalition in support of an initiative reforming alcoholic beverage laws in Washington State. (The initiative was approved by a 59% to 41% margin.) These contributions were not tax deductible under U.S. tax laws.

Costco currently operates 596 warehouses, including 433 in the United States and Puerto Rico, 82 in Canada, 32 in Mexico, 22 in the United Kingdom, nine in Japan, eight in Taiwan, seven in Korea and three in Australia. 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 two additional warehouses in Japan prior to the end of calendar year 2011.

A conference call to discuss these fiscal 2012 first quarter results is scheduled for 8:00 a.m. (PT) today, December 8, 2011, and is available via a webcast on www.costco.com (click on Investor Relations and “Play Webcast”).

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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, uncertainties in the financial markets, 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 costs), energy, and certain commodities, 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.

CONTACTS: Costco Wholesale Corporation

Richard Galanti, 425/313-8203, Bob Nelson, 425/313-8255, Jeff Elliott, 425/313-8264

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COSTCO WHOLESALE CORPORATION

CONDENSED CONSOLIDATED STATEMENTS OF INCOME

(dollars in millions, except per share data)

(unaudited)

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COSTCO WHOLESALE CORPORATION

CONDENSED CONSOLIDATED BALANCE SHEETS

(dollars in millions)

(unaudited)

Subject to Reclassifications