Ultrasonography has been used in clinical fields because of its merits, such as convenience, noninvasiveness and absence of radiation hazard. With improvement of ultrasonographic technology, diagnostic accuracy is increased in detecting gallstone. Authors performed 41 cases of cholecystosonography and compared with surgical and pathological findings. The results are as follows: 1. Demonstration of gallbladder is accomplished in 40 cases out of 41 cases. (97.5%). 2. Gallstone detection rate is 92.5%. False positive rate is 5% an false negative 2.5%. Including one case which turned out C.B.D. stone of false positive detection rate reaches 95%. 3. Diagnostic accuracy of ultrasonography in 17 cases of nonvisualization and faint visualization in oral cholecystogram is 100%. 4. Ultrasonography is essential and highly accurate diagnostic tool in nonvisualized G.B., obstructive jaundice, iodine sensitive and emergency and seriously ill patients.