Over 625 patients having gastric bypass for the treatment of morbid obesity are currently being followed at the University of Iowa. Many innovations have increased operative exposure, greatly reduced operating time, and improved the effectiveness and safety of the operation. Recent weight figures show that a 55 percent loss of excess weight can be expected. Several comparative studies between gastric and jejunoileal bypass show that gastric bypass, while producing identical weight loss, has few of the many complications such as liver failure, renal and gallstone formation, diarrhea, enteritis, that are commonly associated with jejunoileal bypass. Stomal ulcer occurrence has been only 2 percent. Imporvements in diabetes mellitus and hypertension can be expected with weight loss. Other effects of gastric bypass were determined by use of a questionnaire. It is concluded, by surgeons having experience with both gastric and jejunoileal bypass, that gastric bypass is the treatment of choice for morbid obesity when nonoperative measures fail.