This study is based upon our experience with 477 morbidly obese patients who had gastric bariatric surgery during a five-year period. The incidence of biliary tract disease was 39.1%, about four times the incidence in the nonobese population. Intraoperative ultrasonic examination of the gallbladder was done in 50 patients. This technique is a useful adjunct in detecting occult biliary tract disease in morbidly obese patients.