The Authors report their experience in out patient's ambulatory treatment of renal cysts by PCN ultrasound puncture. An aspiration technique is described and the following injection of human fibrin glue after vaporization with sterile alchol 99% in the cyst. Then this technique is compared with other different conventional methods and the clinical results discussed. The data obtained, the excellent compliance of the patients confirm this practice as the best choice in out-patient treatment of this pathology.