Sclerotherapy with 2.5% phenol solution was used to treat 63 hydroceles in 55 patients with a mean age of 69 years. In 51.6% of the patients (32 hydroceles) 1 treatment was sufficient, while 2 treatments were necessary in 25.8% (16 hydroceles), 3 in 13% (8 hydroceles) and 4 in 8% (5 hydroceles). One patient required 7 injections. Treatment was unsuccessful in 1 patient in whom a local allergic reaction developed. Only 1 patient complained of pain, and other complications were rare and mild. On the basis of this experience we concluded that sclerotherapy with phenol 2.5% is a painless, highly effective, safe and economical procedure that permits one to avoid an operation, anesthesia and hospitalization. Its use is warranted in adults and particularly in the elderly.