We compared the safety, excess weight loss (EWL), and improvement in comorbidities after Roux-en-Y gastric bypass (RYGB) in morbidly obese and superobese patients (body mass index, <70 kg/m2 or >or=70 kg/m2). Of 825 patients who underwent RYGB by our group between 1995 and 2003, 79 (9.6%) were superobese (group A) and 746 were morbidly obese (group B). There were significant differences in age (A, 40.8 years; B, 43.2 years; P=0.01), gender (males: A, 40.5%; B, 17.6%; P<0.0001), and type of access (laparoscopic RYGB: A, 4.1%; B, 34.2%; P<0.0001). Sleep apnea (A, 57%; B, 31.4%; P<0.0001) and venous insufficiency (A, 16.5%; B, 2.4%; P<0.0001) were more common in superobese patients. Hospital stay was similar (A, 6.3 days; B, 5.3 days) with adjustment for differences in type of access. Although morbidity was comparable, mortality was higher in the superobese group (A, 2.5%; B, 0.5%; P<0.05). At a comparable follow-up (A, 17.7 months; B, 18.25 months), percent EWL at 1 year was lower in the superobese group (A, 54.6%; B, 64.3%; P<0.0001), but it became similar at 3 years (A, 66.5%; B, 60.7%). Postoperative improvement of comorbidities was equally dramatic in both groups with the exception of venous insufficiency. In conclusion, complications are not increased in the superobese, but they are more often fatal. Superobese patients achieve their maximum weight loss in a longer period of time and reach their nadir at year 3.