Abstract: The application of behavioral concepts to health problems ("behavioral medicine") represents a frontier for behavioral science research for the next decade. Current issues in the field of behavior modification emphasize the relevance of behavioral therapy to lifestyle changes, particularly in the area of health. Behavioral approaches to the etiology, pathogenesis, treatment, and prevention of illness are discussed. Specific topics include cognitive factors in behavior change; coping theory; the psychobiology of smoking; health hazard appraisal; weight loss; child behavior problems; student health; alcohol abuse; mental health; coronary risk behaviors; physical activity; and relapse. Health lifestyle change programs which can be implemented in the community via the mass media are described. Evaluation strategies for health lifestyle programs are also examined, in light of their importance to long term therapeutic success. The theme of maintenance of behavior change is stressed throughout.