Background/Aims: To evaluate the effects of extracorporeal shock-wave lithotripsy(ESWL) on diverse composition-types of gallstones, we conducted an analysis of the characteristics of scanning electron microscopic features of gallstones fragmented by extracorporeal shock waves. Methods: Fifteen gallstones from 1S cholecystectomized patients were fragmented by extracorporeal shock waves in vitro. The fragmented gallstones were studied by gross examination, simple X-ray, microscopic examination, and the scanning electron microscope(SEM). The composition of gallstones was classified by infrared spectrophotometric analysis as cholesterol stone, calcium carbonate stone, and pigment stone. Results; Fifteen gallstones were classified into five groups: three pure cholesterol stones, seven cholesterol stones, two calcium carbonate stones, two hlack pigment stones, and one brown stone. Scanning electron microscopic examination showed that radially oriented clusters of cholesterol crystals and the plane of fracture are parallel to the long axis of the crystals in pure cholesterol stones, intermeshed cholesterol crystals with rounded-border in mixed stones, broken egg-shell-like thin structures in calcium carbonate stones, and irregular bordered and amorphous structures in pigment stones, either black or brown ones. Conclusions: The surface of the gallstone fragments by ESWL showed different SEM patterns according to the type of gallstones, depending on their unique structure and composition. (Korean J Gastroenterol 1995;27:441 - 449)