The Greenville version of the gastric bypass induced long-term remission of type II diabetes mellitus in 121 of 146 (82.9%) morbidly obese patients. Similarly, the operation returned 150 of 152 (98.7%) morbidly obese patients with impaired glucose tolerance to euglycemia. These outcomes were not merely changes in glucose levels; the operation also reduced the mortality and morbidity of the disease. Diabetic patients submitted to surgery had a 1.0% chance of dying during a 10-year period of follow-up compared to a mortality rate of 4.5% in a matched group (p = 0.0003). These results, the best therapeutic outcomes for type II diabetes ever reported, suggest that the disease is not an untreatable, hopeless illness but one that can be treated successfully with better understanding of the pathophysiology of these surgical remissions. The mechanism of the improvement is not yet clear. The rapidity of the correction to euglycemia, usually a matter of days, suggests that the reason is not the loss of weight (i.e., reduction in fat mass) but, rather, the result of the exclusion of food and a secondary alteration in incretin signals from the antrum, duodenum, and proximal jejunum to the islets.