If the physician is to help a patient adopt and maintain "preventive behaviors," the processes that influence and shape both patient and physician behaviors must be understood, the physician's role in the behavioral change process must be acceptable to both the patient and the physician, and an environment that both permits the physician to act and reinforces the physician for acting appropriately must be designed for the physician. A physician's role that is acceptable to both the patient and the physician can be seen as six obligations. The physician must 1) evaluate the medical literature on prevention to determine which services are indicated for which types of patients, 2) when seeing an individual patient, identify the services and behaviors needed by that patient, and 3) advise the patient of the need for action. As the patient responds positively to the physician's advice, the physician must 4) enable and assist the patient to have the indicated tests or procedures and accomplish the suggested behavioral changes, and 5) reinforce the patient's new and ongoing preventive behaviors. The sixth obligation of the physician is to establish, support, and maintain a system to facilitate tasks 2 through 5.