Anorexia nervosa and bulimia nervosa are prevalent illnesses affecting between 1% and 10% of adolescent and college age women. Developmental, family dynamic, and biologic factors are all important in the cause of this disorder. Anorexia nervosa is diagnosed when a person refuses to maintain his or her body weight over a minimal normal weight for age and height, such as 15% below that expected, has an intense fear of gaining weight, has a disturbed body image, and, in women, has primary or secondary amenorrhea. A diagnosis of bulimia nervosa is made when a person has recurrent episodes of binge eating, a feeling of lack of control over behavior during binges, regular use of self-induced vomiting, laxatives, diuretics, strict dieting, or vigorous exercise to prevent weight gain, a minimum of 2 binge episodes a week for at least 3 months, and persistent overconcern with body shape and weight. Patients with eating disorders are usually secretive and often come to the attention of physicians only at the insistence of others. Practitioners also should be alert for medical complications including hypothermia, edema, hypotension, bradycardia, infertility, and osteoporosis in patients with anorexia nervosa and fluid or electrolyte imbalance, hyperamylasemia, gastritis, esophagitis, gastric dilation, edema, dental erosion, swollen parotid glands, and gingivitis in patients with bulimia nervosa. Treatment involves combining individual, behavioral, group, and family therapy with, possibly, psychopharmaceuticals. Primary care professionals are frequently the first to evaluate these patients, and their encouragement and support may help patients accept treatment. The treatment proceeds most smoothly if the primary care physician and psychiatrist work collaboratively with clear and frequent communication.