Background/Aims: Primary intrahepatic stones can usually be distinguished from secondary intra- hepatic stones by the presence of intrahepatic strictures. In Asia, primary hepatolithiasis predo- minates, whereas secondary hepatolithiasis is more commonly found in the West. About 20 years ago, the major chemical element of intrahepatic stones was calcium bilirubinate in Korea. Recently patients with intrahepatic mixed stones which carries high cholesterol content are increasing in Korea. This study indicates our results of systemic analysis on the structure and composition of primary intrahepatic stones. Methods: Multiple intrahepatic stones were harvested by choledochos- copic stone extraction from 84 patients with biliary stricture. We described the external appearance and color of the stones, and then cut the sample stone which was collected from eaclh patient in two pieces. A half of the stone was used for the measurement of chemical compositiion and the rest for electron microscope scanning . The cross sectional appearance was also recorded. Results: Intrahepatic stones were separated as mixed stones in 44 patients(52%) and brown pigiment stones in 40 patients(48%) on the basis of their gross and cross sectional appearance and cholesterol content. The mixed stones had a smooth and distinct black-colored outer shell and a yellow inner body on cross section. The consistency of mixed stoness was hard. The yellow inner body revealed the combination of the radial and concentric pattern. In contrast to the mixed stones, the brown stones were rough surfaced, light to dark brown in shade and soft and friable in consistency. They revealed multiple concentric layers of varying shades of brown on the cross section. In mixed stones, the percentage of cholesterol and calcium bilirubinate was 51.6--6.4% and 24.8 9.1%, respectively. In brown stones, the percentage of cholesterol and bilirubin was 12.5 .5.2% and 42.8 ' 10.2%, respectively. There was a significant difference in the percentage of cholesterol and bilirubin(p 0.001) between mixed stones and brown pigment stones. Conclusions: Primary intrahepatic stones in the past were mainly brown pigment stones. Primary intrahepatic mixed stones in our cases have not been reported in the Korean literature. About a half of our study subjects have had primary intrahepatic mixed stones, which contained high cholesterol <:ontent. We suggest that the chemical composition of primary intrahepatic stones in Korea I.; changing. (Korean J Gastroenterol 1996;28: 85 - 91)