To further define the significance of gallbladder nonvisualization by cholecystosonography, we studied follow-up data on 25 consecutive patients in whom the gallbladder could not be identified despite adequate fasting. In one patient, intravenous cholangiography demonstrated a large gallbladder but no gallstones. In the 24 cases for which a pathoanatomic diagnosis was established, all but two had diseased gallbladders with obliteration of the lumen. This 88% accuracy for positive prediction confirms results of previous sonographic studies and matches the diagnostic significance of nonvisualization at oral cholecystography. We recommend oral cholecystography for all ultrasonic nonvisualized gallbladders for greater diagnostic accuracy when surgery is contemplated.