Prediction of chemical composition of gallstones is a prerequisite in contemplating the chemical dissolution or extracorporeal shock wave lithotripsy of gallstones. The author retrospectively analysed the correlation between the ultrasonography (US) and computed tomography(CT) of 100 consecutive stones obtained from 100 patients were performed under the in vitro condition. Their US and CT fingings were grouped with certain patterns and each group was compared with the chemical composition of the stones. Stones with entirely discernible cirumsference and homogeneous internal echo on US had high bilitubin and low cholesterol content. Acoustic shadows were frequently absent with those stones. Stones with variable internal echo on US had relatively high cholesterol content byt their distribution range were wide. There was no correlation ship beween the cholesterol content and the cT No, of the gallstones. there was positive correlationship beween the calcium content and the cT No. of gallstones, The near totally calcified gallstones had very low cholesterol and high residue content. There was no relationship between the calcification type and the ultrasonographic pattern. In conclusion, those stones with entirely discernible circumsference and homogeneous internal echo on US were pigment stones. On the contrary, stones with variable internal echo had relatively high cholesterol content. CT could predict the calcium content with CT No., but could not predict the cholesterol content.