A prospective study was conducted to evaluate effectivity, problems and adverse effects of extracorporeal shock wave lithotripsy (ESWL) using a newly developed electromagnetic biliary lithotriptor (Lithostar Plus, Siemens, Erlangen, FRG) for the treatment of selected patients presenting with symptomatic cholecystolithiasis. In addition to generally accepted criteria for the selection of patients, gallbladder contractility was established and pigment stones were excluded by computed tomography (CT). 80 out of 486 patients (63 females, 17 males, mean age 36, range 17–76 years) were selected for ESWL using a standardized diagnostic program. 62 out of 80 patients participating in the study had solitary concrements (diameter 23.3 ± 6.4 mm) while in 18 patients 2 or 3 stones (diameter below 10 mm) were observed. Stone fragmentation was achieved after an average of 1.35 treatment sessions (range 1–3) in 78 (97.5%) patients. No clinically relevant adverse effects were observed. Immediately after ESWL, ultrasound revealed misleading results with regard to stone fragmentation. 98.7% of patients (n=77) were seen for follow-up investigations 3, 6 and 9 months after ESWL, and 82% at 12 months. A total of 40 (53%) patients became free of stones. Subgroup analysis showed that 68% of the patients were free of stones (stone diameter 10–20 mm), 54% (20–30 mm) and 33 % (multiple stones), respectively. We therefore conclude that ESWL should be restricted to highly selected patients presenting with small (10–20 mm) solitary c