Problems related to health promotion in primary medical care are reviewed within the framework of five characteristics of current medical practice: physician attitudes and beliefs, the economic structure of medical care, the structure of the medical-care encounter, the state of the art of health promotion, and physician knowledge and skills. The potential for integrating health promotion activities into the primary medical-care environment is based on the principles of pediatrics, general internal medicine, family practice, and obstetrics/gynecology. In the primary-care setting, both the roles and the expectations of physicians and patients are conductive to health promotion activities. Twelve practice principles for the primary physician are discussed, touching on such issues as style of communication, recognition of the "teachable moment," utilization of the longitudinality of the physician-patient relationship, coordination of care, and causes of failure. Issues for the future are reviewed, including the need for restructuring fee schedules, pursuing the knowledge base required for effective health promotion, and integrating training in health promotion methods and techniques in medical school curricula. The complex interactions during the next decade of three trends related to health promotion are discussed as determinants of the role of primary care as a substrate for health promotion.