We treated 97 patients with staghorn calculi by ESWL monotherapy using a Lithostar Lithotriptor (Siemens) between January 1989 and December 1996. Seventeen patients (18 renal units) out of 45 patients (47 renal units) who could be followed up for more than 12 months after ESWL had no stones on radiographs at 3 months after the treatment. The actuarial non-recurrence (or stone-free) rate was 88.9% at 1 year, 79.0% at 3 years, and 63.2% at 5 years after ESWL (Kaplan-Meier method). The actuarial non-regrowth rate (regrowth < 1 mm) was 96.6% at 1 year, 72.8% at 3 years, and 63.7% at 5 years (Kaplan-Meier method). History of urinary stones was a significant risk factor for stone recurrence, while patient sex, affected side, stone number, pyuria (> or = 10/HPF), hydronephrosis on DIP, and staghorn type were not significantly associated with stone recurrence or regrowth (Cox proportional hazard model). Late complications associated with ESWL included renal dysfunction (serum Cr > or = 1.1 mg/dl) in 2 patients, hypertension (> or = 160 mmHg) in 3, and renal atrophy (two-dimensional size < or = 80%) in 5. ESWL exerted adverse effects in a session-dependent manner on the kidney resulting in renal atrophy. Therefore, we highly recommend that ESWL should be limited to less than 10 sessions.