PURPOSE: To evaluate the usefullness of repeated alcohol sclerotherapy for two days through the percutaneous catheter in the treatment of renal cyst. MATERIALS AND METHODS: Repeated sclerotherapies using absolute ethanol(99.9%) were parformed on 20 renal cysts in 18 patients through the indwelling catheter. The cyst volume ranged from 50 ml to 1000ml(mean, 300ml). Under the ultrasound- or CT-guidance, 6F catheter was inserted into the cyst percutaneously. After aspirating the fluid in the cyst, absolute ethanol was injected. While maintaining the catheter for 16-20 hours, at least 3 times of sclerotherapies performed with total procedure time of 30-60 minutes. Follow-up sonography was performed to evaluate the recurrence or collapse of the cysts at 1 and 3 months after the procedure. RESULTS: Among 20 renal cysts, 2 cases were recurred on 1 month follow-up sonography(10%). However, the volumes of recurred cysts were decreased to 40% and 10%, respectively. There was no immediate or delayed complication after sclerotherapy. DISCUSSION: Repeated sclerotherapy for 2 days using absolute ethanol through the percutaneous catheter insertion is a useful method of treatment for renal cyst.