To define the relative merits of radiographic and ultrasonic cholecystography, we studied 208 randomly selected patients with possible cholelithiasis. The patients underwent both procedures, and the results were interpreted in blind fashion. Two hundred patients had satisfactory confirmation of their diagnosis, by either a well visualized radiographic cholecystogram or operation or both. The overall accuracy of the ultrasonic examination was 93 per cent, with a false-negative rate of 11 and an indeterminate rate of 4 per cent. The indeterminate rate was 24 per cent for the single-dose oral cholecystogram and 8 per cent for the double-dose oral cholecystogram. Both ultrasonic cholecystography and radiographic cholecystography are useful to detect gallstones. Our findings support using single-dose oral cholecystography as the routine first examination. If the gallbladder is not satifactorily visualized, ultrasonic cholecystography can be performed immediately. In an emergency or for patients who might be pregnant, ultrasonic cholecystography is available as the initial examination.