In a previous study, Roux-Y gastric bypass was found to be significantly more effective than vertical banded gastroplasty for weight loss in morbid obesity, especially for patients addicted to sweets, probably as a result of dumping syndrome symptoms. This study evaluated the ability to selectively assign nonsweet eaters to vertical banded gastroplasty and sweet eaters to gastric bypass. Compared with random assignment, the percentage excess weight lost at 2 years improved significantly with both groups combined. In the vertical banded gastroplasty group, the percentage increased from 41 +/- 19 to 55 +/- 19 percent. With selective assignment, the percentage excess weight lost with gastric bypass was still better than that with vertical banded gastroplasty. Weight loss with gastric bypass was still superior to that of vertical banded gastroplasty but at the expense of more complications. Gastric bypass was ineffective in 19 percent of the super obese patients. A combined restrictive, malabsorptive procedure may be necessary in such persons.