Since 1977, we have managed 56 patients (36 Payne and 20 Scott bypasses) with late (one to 18 years) complications resulting from a jejunoileal bypass. All patients underwent a one-stage conversion of the jejunoileal bypass to a gastric bypass. Patients were classified according to postbypass weight, the need for nutritional support, the type and severity of complication, and the time interval between jejunoileal bypass and the onset of the complication and correction of the complication. There were no operative deaths; one patient died 18 months after surgery of cirrhosis. The complication rate was 34%; however, most complications were minor. Our experience with this procedure has shown it to be highly effective in correcting complications other than polyarthritis. When coupled with nutritional support, it is safe even in malnourished patients.