We analyzed findings of sonography and ERCP retrospectively to compare the diagnostic accuracy of sonography with ERCP in patients suspected with biliary stones. 88 patients underwent surgery who had studied with sonography and ERCP were evaluated in order of intrahepatic duct, extrahepatic duct and gall bladder. Of these patients, 80 cases were proved biliary stones. Sonography correctly diagnosed 19 of 19 patients with intrahepatic duct stones, 32 of 40 patients with extrahepatic duct stones and 35 of 41 patients with gall stones with sensitivities of 100%, 80% and 85% respectively. ERCP correctly identified 14 of 18 patients with intrahepatic duct stones.26 fo 37 patients with extrahepatic duct stones and 15 of 33 patients with gall stones with sensitivities of 78%, 70% and 45% respectively. Our results shows sonography is more sensitive to detect stones of biliary system than ERCP.