One hundred and thirteen morbidly obese patients underwent bariatric surgery. Mean preoperative percentage above ideal weight was 98.3% (SD 30.0%). Mean percentage above ideal weight eighteen months after operation was 19.5% (SD 23.8%). Fifteen patients (13.3%) required pre-operative weight loss because of respiratory dysfunction and raised PaCO2. One patient developed asthma in the postoperative period. There were no other clinical postoperative respiratory complications. 40% of patients however did show radiological evidence of basal pulmonary atelectasis on the initial postoperative chest X-ray. All patients had pre-operative cardiological screening: there were no cardiac complications except one case of atrial fibrillation. One patient suffered a proven pulmonary embolus and recovered. Six patients (5.3%) required correction of a pre-operative potassium deficit. No episode of gastric acid aspiration syndrome occurred. 58% of patients presenting for obesity surgery had identifiable psychopathology. Despite strict pre-operative psychiatric screening, 15% of patients coming to operation required postoperative psychiatric management.