In order to determine the value of Computed tomography(CT) in the diagnosis of choledocholithiasis, the autoors retrospectively studied 33 cases of choledocholithiasis proven by surgery from January 1983 to June 1985. Among them, 15 cases were examined by both Ct and ultrasonography. The results were as follows : 1.There were 12 men and 21 women with mean age of 57 years. 2 . CT correctly diagnosed choledocholithiasis in 29(88%) of total 33 cases. These were 4 false negativ ediagnoses and there were no false positive. 3. in 15 cases which were examined by both CT and ultrasonography, 13(86%) cases were correctly diagnosed by CT and 7(46%) by ultrasonogrphy. 4. The majority (88%) of choledocholithiasis were demonstrate as calcific censity and 4 cases (12%) were nealry isodense to pancreas. 5. Most cases were shown as homogenous density and 5 cases (16%) as ringlike structure with low density center and high density periphery. 6. Additional findinsg. such as intrahepatic and or GB stones. pericholangitic abscess, GB empyema, ascites, and liver cirrhosis were also identified by CT. 7. CT is effective for noninvasive and accurate detection of choledocholithiasis. So invasive cholangiography, such as E.R.C.P or P.T.C can be reserved in many cases of choledocholithiasis.