OBJECTIVE: We evaluated the safety and effectiveness of multiple-session percutaneous sclerotherapy with 95% sterile alcohol for symptomatic simple renal cysts. MATERIALS AND METHODS: From March 1998 to September 2001, 19 patients with large symptomatic renal cysts underwent percutaneous aspiration with or without sclerotherapy. Seven patients underwent simple aspiration only, and 12 received 3 sessions of sclerotherapy with 95%sterile alcohol after aspiration of the cystic fluid. In the sclerotherapy group, alcohol was injected into the renal cysts and retained for 60 minutes in each session; this was then repeated twice at 24-hour intervals. RESULTS: The mean follow-up period was 11 (range, 3 to 21; median, 10) months, the mean cystic diameter was similar in the aspiration therapy group and the sclerotherapy group (65vs. 7.3 cm, p = 0.30). In the aspiration therapy group, the mean reduction in cystic diameter was 21%, and no patient had a reduction of cystic diameter of more that half of the original diameter. In the sclerotherapy group, the mean reduction in cystic diameter was 96%. All patients (100%) had a reduction of cystic diameter of more than half, and 11 (86%) had complete cyst regression. No complications were noted in either treatment group. CONCLUSION: Multiple-session percutaneous sclerotherapy with 95%sterile alcohol for symptomatic simple renal cysts in safe, cost-effective, and well tolerated by most patients. It can be used as first-line treatment.