The accuracy and possible clinical value of grey scale ultrasonography in the detection of gallstones has been prospectively studied in 100 unselected patients presenting with recurrent biliary colic, acute cholecystitis or acute pancreatitis. Adequate visualization of the gallbladder was obtained in 79 cases, with 3 false positive and no false negative reports. Oral cholecystography remains the initial investigation of choice in patients presenting with recurrent biliary colic, but grey scale ultrasound has been shown in this study to be a reliable means of detecting gallstones in the 'acute' situation, when conventional contrast radiology is of limited value.