In this study the results of two percutaneous treatment of simple renal cysts are compared: aspiration alone versus aspiration and ethyl alcohol injection. Out of 40 patients, 17 have been treated with aspiration only and 23 with aspiration and ethanol injection. Recurrent disease has been observed in 88.2% of patients in the aspiration group and 30.4% in the aspiration and ethanol injection group. This difference is statistically significant as shown by the Kaplan-Mayer curve when evaluated by the Log-rank test, and this is sufficient to justify such treatment as a first quality choice.