The eating disorders, a group of conditions that affect primarily adolescents and young adults, increased significantly in prevalence during the last 3 decades. Marked by a combination of medical and psychological factors in their etiology and outcome, they include predominantly the well-known entities of anorexia and bulimia nervosa. Anorexia nervosa is viewed most simply as the purposeful loss of weight beyond a healthy state, whereas bulimia nervosa is marked by recurrent episodes of binge eating along with purging behaviors. The diagnosis and prevalence of these disorders are much debated, and many questions remain about their etiology and outcome. Nevertheless, the growing incidence and prevalence of eating disorders in adolescents and adults requires that the primary care physician has some knowledge of the principles involved in the evaluation and treatment of both anorexia and bulimia nervosa essential for the primary care physician.