A report is presented on 82 gastric bypass operations performed from 1979 to 1988. The average preoperative body weight was 132 kg, the body mass index (BMI) 45.0 +/- 7.0. 1 patient died (mortality 1%). 88 per cent of all patients were followed up 2 months to 9 years (2.5 years on average) postoperatively. The mean weight loss was 40.8 kg (reduction of BMI 15.1). Obesity-related diseases decreased remarkably, 3 stomal ulcers and 5 cases of anemia occurred as late complications. On the basis of these results gastric bypass is shown to be an effective and safe treatment of morbid obesity.