In vitro fragmentation of gallstones was performed by means of ultrasound (n = 89) and electrohydraulic lithotripsy (n = 83) with success rates of 100% and 93%, respectively. The fragmentation time was 21.9 +/- 52 seconds (mean +/- SEM) for ultrasound and 2.5 +/- 3.4 seconds for electrohydraulic lithotripsy. The energies required were similar to those used safely in the fragmentation of renal and bladder stones. Fragmentation was not related to the composition of the gallstones; there was no statistical difference between the fragmentation times or rates (p greater than 0.05) in cholesterol stones and pigment stones by either method. Fragmentation time was linearly related to gallstone weight for both methods. Comparison of ultrasound and electrohydraulic lithotripsy, using the two-way analysis of variance model, revealed no statistical difference between the two methods in times and rates of fragmentation (p greater than 0.05). Both ultrasound and electrohydraulic lithotripsy offer distinct advantages over the dissolution of gallstones by chemical methods because they are rapid and independent of gallstone composition. In vivo fragmentation of a large pigment common duct stone was also accomplished by means of an electrohydraulic lithotriptor. The stone was discovered in a 79-year-old patient on post-operative T-tube cholangiogram. Chemical analysis of the gallstones removed from the patient during cholecystectomy had revealed a very low cholesterol content. Since the remaining stone could not be dissolved and was too large to be mechanically extracted, it was fragmented through a T-tube, under fluoroscopic guidance and the small fragments were extracted with a dormia basket. The electrohydraulic lithotriptor was selected because it has a flexible probe.