Group Health Cooperative of Puget Sound (Seattle, WA) believes that wise purchasing practices contribute both to cost efficiency and high quality healthcare delivery. At Group Health Cooperative, we came by this belief through a variety of forces all pushing for healthcare reform--legislative-, market-, and consumer-driven forces. At nearly fifty years of age, Group Health Cooperative of Puget Sound is the oldest health maintenance organizations (HMO) in the country. As in the beginning, Group Health is still a consumer-governed cooperative that has grown to over 400,000 enrollees, 44,000 of whom are seniors. The Co-op has a mixed staff/group/network physician model. Its 1994 budget was over $1 billion, with Medicare revenue accounting for about 30% of the budget. For nearly its first four decades, Group Health was just about the only show in town. If you wanted prepaid healthcare or independent consumer oversight for quality of care, you joined Group Health. But by the mid-1980s, there were over twenty other managed care competitors. Some were local health plans with a sideline managed-care business, but, increasingly, competitors included huge, national, for-profit corporations. In addition, two other streams of change pressured healthcare in the Seattle area and elsewhere--legislative and market reform. In Washington, legislative reform started in 1989 with the Basic Health Plan, a program to aid the working poor by subsidizing their healthcare insurance premiums based on financial need.(ABSTRACT TRUNCATED AT 250 WORDS)