One hundred and seven patients with caliceal stones causing flank pain were treated by extracorporeal shock wave lithotripsy (ESWL), followed up and reviewed. The total stone-free rate 3 months after ESWL was 38.8%. The total pain-free rate was 50.5%. The pain-free rate was 85% in the stone-free group and 29% in the group with residual stones. No significant differences between the stone-free rate and the duration of pain or age was noted. Patients with abnormal intravenous pyelography (IVP) had a lower stone-free rate than patients with normal IVP (16 vs. 45%, p less than 0.05). The complications included: 6 cases of stone street formation with spontaneous passage; 1 case of stone street formation needing percutaneous nephrolithotomy for drainage; 1 perirenal hematoma; 9 cases of severe colic pain following ESWL; 3 cases of fever following ESWL, and 4 cases of hydronephrosis due to a stone in the ureterovesicle junction. These results show that ESWL is an effective, noninvasive treatment for painful caliceal stones.