A review of the results of the evaluation of the gallbladder by gray scale ultrasonography in 52 patients is presented. When the gallbladder was successfully identified by ultrasound (46 patients) the detection of stones was 98% accurate. When the gallbladder was not identified (four patients), a contracted gallbladder containing numerous stones was found at operation. The left lateral decubitus position proved very helpful in displaying the gallbladder when it could not be identified in the standard supine position. Ultrasonic evaluation of the gallbladder is of most value in the patients who have had unsuccessful radiographic studies.