The role of gallbladder emptying in fragment disappearance following shock wave lithotripsy of gallstones is poorly understood. We studied gallbladder motility in two groups of patients who had been treated by electrohydraulic shock wave lithotripsy and bile acid dissolution therapy. Group I (n = 20) consisted of patients with fragment disappearance within 18 months after lithotripsy, while patients in group II (n = 20) still harboured fragments in the gallbladder 18 months after lithotripsy. Fasting gallbladder volume was 19 +/- 10 ml (mean +/- S.D.) in group I, and 24 +/- 12 ml in group II (not significant). The residual volume was 8 +/- 9 ml in group I, but 18 +/- 14 ml in group II (p < 0.005). Thus, patients in group I ejected nearly twice as much of the fasting gallbladder volume as patients in group II. This difference in gallbladder emptying was still present if only the patients with single stones were compared in both groups. From the results of this retrospective study we conclude that gallbladder emptying is an important factor for complete fragment disappearance after gallstone disintegration by extracorporeally generated shock waves. Further prospective studies are needed to confirm these observations.