Nonsurgical methods fail to maintain clinically significant weight loss greater than or equal to 5 y in severely obese patients. Vertical banded gastroplasty and Roux-Y gastric bypass are the main operations for obesity. Modifications of intestinal bypass reserved for special cases require particular expertise in long-term management. Operations function by inducing satiety, nimiety, or aversion. Optimal weight loss or goal weights have not been defined and outcome predictors are inadequate. Results depend more on motivation and behavior than on metabolic, gastrointestinal, or technical factors. New approaches such as adding vagotomy or using inflatable cuffs to adjust outlet size in gastroplasty or modifying outlets or segment lengths in gastric bypass might improve long-term results. A staged approach to surgical treatment of obesity is proposed. Surgery will persist as a viable treatment alternative for severe obesity until effective preventive measures are taken to reduce the prevalence of this serious disease.