With the evolution of minimally invasive approaches in medicine, phenol has regained its popularity for the sclerotherapy of testicular hydroceles. Together with reported efficiency and safety of 2.5% phenol in the literature, the recently proved safety of 3% phenol in esophageal variceal sclerotherapy has led us to perform a prospective study to lessen the number of sessions. Sclerotherapy with 3% aqueous phenol was applied on an ambulatory basis to 23 patients with 31 hydroceles, who were over 40 years old and who had no fertility problems. The over-all cure rate was 96% with an average follow-up of 3 years, and 58% of the hydroceles required only one session of treatment. The average number of treatment sessions was 2.2 (range; 1-7). One patient with a history of herniorraphy 10 years earlier, was treated surgically following failure of seven sclerotherapy sessions. Phenol, a sclerosant superior to other conventional agents including tetracyclines, requires neither anesthetics nor prophylactic antibiotics. Our findings indicate that sclerotherapy with 3% phenol is an effective, economical and safe form of therapy for patients with hydrocele.