Bariatric surgery is performed for clinically severe obesity and includes jejunoileal bypass, which is designed to produce weight loss through malabsorption, and the gastric restrictive operations--gastric bypass, gastrogastrostomy, and gastroplasty--which produce weight loss through restriction of volume of intake. Patients have problems after bariatric operations because of knowledge deficits; attitudinal, social, and psychologic influences; and anatomic and physiologic effects of these operations. Specific difficulties specific to the type of bariatric operation may arise. Although certain complications may be averted with nonoperative therapy, reversal of the operation may be required for others.