OBJECTIVE: To compare the safety, excess weight loss (EWL) and improvement of obesity-related disorders after Roux-en-Y gastric bypass RYGBP in morbidly obese (BMI < 70 Kg/m²) and superobese patients (BMI ³70 Kg/m²). METHODS: Since 1995, a total of 825 morbidly obese patients underwent RYGBP in our institution. There were 79 (9.6%) patients (group A) with a BMI ³ 70 Kg/m² and 746 patients (group B) with a BMI < 70 Kg/m². Patient demographics, operative morbidity and mortality, % EWL and improvement of obesity-related disorders were prospectively collected in a database. RESULTS: A laparoscopic access was used in 261/825 patients (31.6%). There was a significant difference in age (A: 40.8 vs. B: 43.2 years, p=0.01), gender (% males, A: 40.5% vs. 17.6%, p<0.0001) and type of access (% laparoscopic RYGBP, A: 4.1%, B: 34.2%, p<0.0001) between superobese and morbidly obese patients. American African race was more common in the superobese group (A: 21.2% vs. B: 12.6%) but it did not reach statistical significance. Although there was no significant difference in morbidity between the two groups, mortality was higher in the superobese group (A: 3.8% vs. B: 0.5%, p=0.02). Laparoscopic access had no impact on the outcome of RYGBP except for a shorter LOS (A: 6.2 vs. B: 4.9 days, p=0.001) in favor of the morbidly obese group. Mean follow-up was similar in both groups (A: 17.7 vs. B: 18.2 months). %EWL at 1-year was significantly lower in the superobese group (A: 54.6% vs. B: 64.3%, p<0.0001) but there was no difference at 3 years (A: 66.5% vs. 60.7%). Preoperative incidence of sleep apnea (A: 57% vs. B: 31.4%, p<0.0001) and venous stasis dermatitis (A: 16.5% vs. B: 2.4%, p<0.0001) was significantly higher in the superobese group, but postoperative improvement of all obesity-related disorders was similar in both groups. CONCLUSION: Complications are not increased in the superobese but they are more often fatal. Weight loss in the superobese is slower, but it continues beyond the first year. RYGBP in the superobese is as effective as in the morbidly obese in resolving, or improving obesity-related disorders.