This article examines an advanced managed care area, the San Francisco East Bay Area in California, for basic organizational issues posed by managed care for the medical profession. Of the three basic structures found, the independent practice association (IPA) model is theoretically most promising. Unlike the integrated health plan, the IPA seeks to retain traditional practice autonomy. Unlike the isolating direct gatekeeper model, the IPA assembles physicians in self-directed groups to invent and implement solutions and to exert political influence upward. In practice, however, it has proved difficult to balance practice autonomy with IPA authority. Both large, successful East Bay Area IPAs show signs (perhaps inevitably) of favoring authority over autonomy, as shown by their policies on governance, membership, and administration. Several policies are suggested to help redress this balance. Medical leaders must act now, before all the evidence is in, or the institutions of the past--hospitals and insurance companies--will control our future.