Aim: To evaluate the efficacy of a new sclerotization technique with pure ethanol in the treatment of symptomatic renal cysts. Patients and Methods: Fourteen patients having renal cysts with a meant diameter of 10 (range 5–15) cm were treated. Our technique includes: ultrasound-guided percutaneous puncture with an 18-gauge needle, positioning of a 5-Fr catheter, complete cyst fluid aspiration, injection of pure alcohol equal to 15% of the initial cyst volume, and alcohol aspiration after 90 min. The procedure was repeated eight times within 5 days. The patients were followed up by ultrasound and/or CT scan for 1 year. Results: All patients became symptom free. Follow-up showed a progressive reduction of the cyst diameter in all cases. Three cysts only (in 2 patients; cyst diameter <2 cm) persisted after 12 months. No significant complications were observed. Conclusions: In our experience, injections of pure ethanol in renal cysts, repeated after some days, were effective in eliminating recurrences and related symptoms. The procedure was not associated with significant complications. Our findings suggest that it be considered the first-choice procedure in the treatment of renal cysts, due to the good results and the low cost of ethanol.