Bariatric surgery leads to sustainable long-term weight loss and may be curative for such obesity-related comorbidities as diabetes and obstructive sleep apnea in severely obese patients. The Roux-en-Y gastric bypass has become the most common procedure for patients undergoing bariatric surgery. The procedure carries a mortality risk of up to 1 percent and a serious complication risk of up to 10 percent. Indications include body mass index of 40 kg per m2 or greater, or 35 kg per m2 or greater with serious obesity-related comorbidities (e.g., diabetes, obstructive sleep apnea, coronary artery disease, debilitating arthritis). Pulmonary emboli, anastomotic leaks, and respiratory failure account for 80 percent of all deaths 30 days after bariatric surgery; therefore, appropriate prophylaxis for venous thrombo-embolism (including, in most cases, low-molecular-weight heparin) and awareness of the symptoms of common complications are important. Some of the common short-term complications of bariatric surgery are wound infection, stomal stenosis, marginal ulceration, and constipation. Symptomatic cholelithiasis, dumping syndrome, persistent vomiting, and nutritional deficiencies may present as long-term complications.