This study assessed the ability of biochemical tests and ultrasound to predict the presence of ductal calculi, and thereby refine the indications for ERCP, in patients before or after laparoscopic cholecystectomy. Thirteen of fifty-three patients investigated before laparoscopic cholecystectomy, and four of seventeen investigated after had stones confirmed at ERCP. The most sensitive indices for stones were raised serum alkaline phosphatase (0.76), aspartate transferase (0.75) and alanine transferase (0.76). The most specific indices were an abnormal ultrasound (0.92), raised serum amylase (0.78) and raised bilirubin (0.75). Serum bilirubin, amylase and ultrasound were all normal in twenty-seven patients and all of these had normal ERCPs. If patients with normal bilirubin, amylase and ultrasound were not referred for ERCP, no stones would have been overlooked and the number of ERCPs could have been reduced by 39%.