Managed care plans now enroll 38.6 million persons in the United States, and have increased their enrollment 14-fold in 5 years. The three major health reform proposals before Congress presently make managed care organizations, in one form or another, the linchpin of their reform plans. The authors trace the history of managed care leading to today's spectrum of plans from health maintenance organizations to preferred provider organizations with all their variants. They examine the government and insurance industry records of successes and failures and project the future for managed care with and without government-imposed healthcare reform. They unscramble the "alphabet soup" and detail the problems physicians have encountered in managed care settings. Given the key role of the primary care physician, the authors urge osteopathic physicians to take a proactive role in designing the shift to managed care. By supporting intelligent healthcare reform that brings physicians, hospitals, and insurers together in a practitioner-friendly system, the primary care physician can assume the leadership role in managed care and continue to serve as the patient advocate.