We used high-resolution real-time ultrasonography to examine the gallbladder in patients with signs and symptoms suggestive of gallbladder disease. Using this noninvasive technique, the physician can examine the gallbladder and related anatomy thoroughly in less than five minutes. The technique is much easier to learn and perform than gray-scale ultrasonography. In 313 patients in whom gallstones were later confirmed at cholecystectomy or autopsy, the ultrasound examination achieved an accuracy of 96 per cent in the evaluation of cholelithiasis. Five examinations gave false-negative results, one a definite false-positive result, and two possible false-positive results; six examinations were inadequate. The sensitivity of the method was 98 per cent, and the specificity was between 93.5 and 97.7 per cent. In 124 patients evaluated prospectively by means of both ultrasound and oral cholecystography, the ultrasound study revealed calculi in five patients in whom calculi were not demonstrated on an adequate oral cholecystogram. No calculus detected with oral cholecystography was missed by ultrasound. We believe that ultrasound should replace oral cholecystography as the first technique in evaluation of the patient with suspected gallbladder disease.