Massive obesity is associated with serious co-morbidities. After failure of extensive conservative measures, surgical procedures have developed as the only successful method for sustained weight loss. Criteria for operation are: presence of serious diseases associated with morbid obesity; greater than 45 kg above ideal weight or body mass index greater than 40 kg/m2 for usually greater than 5 years; failure of sustained weight loss on extensive conservative regimens; commitment to lifelong follow-up; and acceptable operative risk. Angina pectoris itself is not a contraindication to these operations. Patients who do not quite meet the weight criteria may still be candidates for an obesity operation in certain instances, e.g., debilitating musculoskeletal pains in weight-bearing joints, diabetes, significant hypertension, reflux esophagitis, urinary stress incontinence. Although current operations result in lasting weight loss of greater than 50% of excess weight in the majority of patients, the surgical candidate must understand and accept the principles of the procedures, the potential for serious complications, the dietary necessities, and occasional failures.