This chapter focuses on bariatric surgery patients. It considers the late complications following the most commonly performed procedures: Roux en Y gastric bypass (RYGB), laparoscopic adjustable gastric band (LAGB), vertical-banded gastroplasty, and biliopancreatic diversion (BPD). Incisional hernias are a potential complication of most operations. Another common complication after the significant weight loss following bariatric surgery is the development of gallstones. The major complications following LAGB include band slippage or erosion, gastric prolapse, port/tubing malfunction, pouch/esophageal dilation, esophagitis and infection. Obese patients sustain greater risks when undergoing any surgical procedures, due to both co-morbidities and anatomic factors. Bariatric surgery confers multiple benefits including weight loss, resolution of co-morbidities, and potentially improved quality of life. Knowledge of the technical details as they relate to the potential complications of each bariatric procedure is critical for early diagnosis and treatment, allowing patients to benefit optimally from their weight loss.