Severe obesity is associated with multiple comorbidities and is refractory to dietary management with or without behavioral or drug therapies. There are a number of surgical procedures for the treatment of morbid obesity, including purely gastric restrictive, a combination of malabsorption and gastric restriction or primary malabsorption. The purely gastric restrictive procedures, including vertical banded gastroplasty and laparoscopic adjustable silicone gastric banding, do not provide adequate weight loss. African-American patients do especially poorly after the banding procedure with the loss of only 11% of excess weight in one study. Gastric bypass (GBP) is associated with the loss of 66% of excess weight at 1 to 2 years after surgery, 60% at 5 years and 50% at 10 years. For unknown reasons, African-American patients lose significantly less weight than Caucasians after GBP. There is a risk of micronutrient deficiencies after GBP, including iron deficiency anemia in menstruating women, vitamin B12, and calcium deficiencies. Prophylactic supplementation of these nutrients is necessary. Recurrent vomiting after bariatric surgery may be associated with a severe polyneuropathy and must be aggressively treated with endoscopic dilatation before this complication is allowed to develop. The malabsorptive procedures include the partial biliopancreatic bypass (BPD) and BPD with duodenal switch (BPD/DS). The BPD appears to cause severe protein-calorie malnutrition in American patients; the BPD/DS may be associated with less malnutrition. Weight loss failure after GBP does not respond to tightening a dilated gastrojejunal stoma or reducing the size of the gastric pouch. These patients may require conversion to a malabsorptive distal GBP, similar to the BPD. However, because of the risk of severe protein-calorie malnutrition and calcium deficiency BPD should be reserved for patients with severe obesity comorbidity. The risk of death following bariatric surgery is between 1% and 2% in most series but is significantly higher in patients with respiratory insufficiency of obesity. In most patients, surgically induced weight loss will correct hypertension, type II diabetes mellitus, sleep apnea, obesity hypoventilation syndrome, gastroesophageal reflux, venous stasis disease, urinary incontinence, female sexual hormone dysfunction, pseudotumor cerebri, degenerative joint disease pains, as well as improved self-image and employability.