THE CORPORATE LIBRARY

Related Party Transactions and Outside Related Director Information

Costco Wholesale Corporation (COST)

12/20/2005 Proxy Information

John W. Meisenbach is a principal shareholder of MCM, A Meisenbach Company. MCM provided consulting and brokerage services in managing the CompanyŐs employee benefit and member insurance programs. Employee medical, life and disability benefits, together with member health insurance premiums totaled $541,904,298. For these services, MCM received total compensation from third-party insurers of $2,380,543 in fiscal 2005.

Richard D. DiCerchioŐs son and brothers-in-law were employed by the Company during fiscal year 2005 at annual salaries of $83,377, $195,750 and $86,847, and received grants of 2,250, 8,000, and 2,250 options, respectively. Richard M. LibensonŐs daughter and son were employed by the Company during fiscal year 2005 at annual salaries of $82,156 and $60,000, respectively, and the former received a grant of 2,250 options. James D. SinegalŐs son and brother-in-law were employed by the Company during fiscal year 2005 at annual salaries of $266,209 and $216,541, and received grants of 37,500 and 18,750 options, respectively. Salary amounts include bonuses. Options were granted at an exercise price of $43.79, subject to vesting over five years and an expiration period of ten years. These individuals also participate in benefit plans available to employees generally. No family members of executive officers or directors are executive officers of the Company.

During fiscal year 2005, a company controlled by one of Mr. SinegalŐs sons (who is not employed by the Company) sold merchandise to the Company for resale, for which the Company paid $1,351,826.

These relationships and transactions were approved by the Audit Committee.

12/20/2004 Proxy Information

John W. Meisenbach is a principal shareholder of MCM, A Meisenbach Company. MCM provided consulting and brokerage services in managing the CompanyŐs employee benefit and member insurance programs. Employee medical, life and disability benefits, together with member health, auto and homeowner insurance premiums, totaled $671,537,736. For these services, MCM received total compensation from third-party insurers of $1,795,209 in fiscal 2004.

Richard D. DiCerchioŐs son and brothers-in-law were employed by the Company during fiscal year 2004 at annual salaries of $86,068, $203,704 and $87,260, respectively. Richard M. LibensonŐs daughter was employed by the Company during fiscal year 2004 at an annual salary of $89,713. James D. SinegalŐs son and brother-in-law were employed by the Company during fiscal year 2004 at annual salaries of $264,054 and $222,716, respectively. No family members of executive officers or directors are executive officers of the Company.

A company controlled by one of Mr. SinegalŐs sons (who is not employed by the Company) sold merchandise to the Company for resale, for which the Company paid $1.16 million.

Jeffrey H. Brotman is a co-founder of Costco Wholesale Corporation.

12/18/2003 Proxy Information

John W. Meisenbach is a principal shareholder of MCM, A Meisenbach Company. MCM provided consulting and brokerage services in managing the CompanyŐs employee benefit and member insurance programs. Employee medical, life and disability benefits, together with member health, auto and homeowner insurance premiums, totaled nearly $552 million. For these services, MCM received total compensation from third-party insurers of $1,633,857 in fiscal 2003.

Richard D. DiCerchioŐs son and brothers-in-law were employed by the Company during fiscal year 2003 at annual salaries of $75,102, $170,823 and $84,115, respectively. Richard M. LibensonŐs daughter was employed by the Company during fiscal year 2003 at an annual salary of $78,444. James D. SinegalŐs son and brother-in-law were employed by the Company during fiscal year 2003 at annual salaries of $215,120, and $190,001, respectively. No family members of executive officers or directors are executive officers of the Company.