A prospective, randomized trial comparing vertical banded gastroplasty (VBG) and vertical gastric bypass (GB) for obesity was completed in 106 patients who did not differ in baseline body mass index (BMI = kg/m2) or length of follow-up. The goal of this surgery was to return patients to within 50% of their ideal weight, i.e., a body mass index less than 35 kg/m2, and to accomplish this while maintaining a low risk for malnutrition as well as other morbidity and mortality. Success was defined as a BMI less than 35 kg/m2 because the mortality risk increases rapidly above this degree of obesity. Surgical failures were encountered in 43% of the 54 patients in the VBG group, all of whom had division between the vertical staple lines. The main causes of failure were stenosis and enlargement of the gastroplasty orifice. Surgery failed in 23% of the GB-treated patients, due to perforation of the vertical staple line. An isolated gastric bypass (IGB) not dependent on staples was performed as the remedial operation for the failures of both VBG and GB. IGB was significantly better than VBG or GB, with a success rate of 83% compared with 39% for VBG and 58% for GB. Subsequent experience since completion of this randomized trial in 54 consecutive patients supports IGB for primary, as well as remedial, operations for the morbidly obese (BMI = 40 to 50 kg/m2), as well as for patients who are super obese (BMI greater than 50 kg/m2).