Antitrust laws place significant limits on collective action among independent practicing physicians. The lawful options most likely to appeal to physicians include the complete merger of physician practices or the significant involvement of a physician or group in a partially integrated legitimate joint venture, such as a provider-sponsored PPO. Neither activity should be undertaken without the assistance of legal counsel. Change in the overall thrust of antitrust law is unlikely, and physicians must protect themselves from liability through careful business planning and the use of competent legal counsel.