Of 31 boys 10 to 16 years old referred for treatment of a left grade II or III varicocele 28 underwent percutaneous sclerotherapy. Due to anatomical and technical obstacles sclerotherapy was not possible in 3 boys. At follow-up 1 of 16 boys (6.2 per cent) had a mild recurrence detected by Doppler sonography of the spermatic cord. Percutaneous sclerotherapy had no serious side effects, and proved to be an efficient and convenient treatment of left varicocele in childhood.