Twenty-eight patients with 30 symptomatic simple renal cysts were treated by percutaneous aspiration of the cyst and injection of 95% ethanol. All patients were available for follow-up during mean period of 19 (range 14-40) months. In all patients, successful resolution of the cyst with disappearance of the symptoms was observed within 1 month after treatment. During the whole period of follow-up, no patient experienced recurrence of symptoms or required repeat therapy. Of all renal cysts treated, resolution was complete in 25 (83%) and partial (recurrence of < 50% of original cyst volume with no symptoms) in 5 (17%). The degree of response to sclerotherapy (whether complete or partial) correlated significantly with cyst size (P > 0.0008). Major complications were not encountered, while microscopic hematuria was seen in two patients, and low-grade fever was observed in another two. Ethanol sclerotherapy is simple, noninvasive, and highly cost-effective and should be recommended for the treatment of symptomatic simple renal cysts.