This article examines the psychological and physiological concomitants of obesity and presents practical methods for working with obese patients. Three areas of physiology are covered: fat cell theory, set point theory, and dietary obesity. The social and emotional consequences of obesity are discussed, as are the psychological stages experienced by both patients and professionals during a typical course of weight reduction. Screening is a most important aspect of a program. There are several methods for determining which patients will profit from treatment. Recent advances in treatment include a focus on physical activity, improvements in behavior modification, and the development of aggressive methods for promoting weight loss in moderately and morbidly overweight persons. Finally, social support is discussed, because the social context in which a program is administered may be more important than the nature of the program itself.