OBJECTIVE: To complete a long-term (>10 years) follow-up of patients undergoing isolated roux-en-Y gastric bypass for severe obesity. BACKGROUND: Long-term results of gastric bypass in patients followed for longer than 10 years is not reported in the literature. METHODS: Accurate weights were recorded on 228 of 272 (83.8%) of patients at a mean of 11.4 years (range, 4.7-14.9 years) after surgery. Results were documented on an individual basis for both long- and short-limb gastric bypass and compared with results at the nadir BMI and % excess weight loss (%EWL) at 5 years and >10 years post surgery. RESULTS: There was a significant (P < 0.0001) increase in BMI in both morbidly obese (BMI < 50 kg/m) and super obese patients (BMI > 50 kg/m) from the nadir to 5 years and from 5 to 10 years. The super obese lost more rapidly from time zero and gained more rapidly after reaching the lowest weight at approximately 2 years than the morbidly obese patients. There was no difference in results between the long- and short-limb operations. There was a significant increase in failures and decrease in excellent results at 10 years when compared with 5 years. The failure rate when all patients are followed for at least 10 years was 20.4% for morbidly obese patients and 34.9% for super obese patients. CONCLUSIONS: The gastric bypass limb length does not impact long-term weight loss. Significant weight gain occurs continuously in patients after reaching the nadir weight following gastric bypass. Despite this weight gain, the long-term mortality remains low at 3.1%.