Ultrasonography, although an accurate method of detecting stones within the gall bladder, is unreliable for the detection of bile duct stones for which per-operative cholangiography remains the standard investigation. Fifty seven patients undergoing elective cholecystectomy had both a pre-operative intravenous cholangiogram and per-operative cholangiography. The pre-operative investigation is shown to be at least as effective in the detection of common bile duct stones and only missed a duct stone in one patient. The substitution of pre-operative intravenous cholangiography for routine per-operative cholangiography would result in a significant reduction in operating time, may provide advance knowledge on the biliary anatomy and would allow advance planning of the likely procedure. It is suggested that pre-operative intravenous cholangiography, carried out on the day of admission, should be considered as a preferred alternative investigation to per-operative cholangiography.