The problem of patient compliance, as well as the ability of the physician to understand, detect, and improve compliance are described in relation to a new model of health decisions and patient behavior. The health decision model combines decision analysis, behavioral decision theory, and health beliefs. This model provides a framework for modifying general health beliefs; treatment recommendations; experience with therapeutic regimens and health care providers; patient knowledge and social interaction patterns. Physicians, guided by certain ethical restraints, are in a unique position of responsibility and opportunity to actively encourage patient compliance with treatment.