Since 1970 we perform the prophylactic operation of grade II and III varicocele during childhood and puberty, even if there were overtreatment. Varicocele may very early interfere with testicular development and already causes histological changes in boys at the beginning of puberty. We have made a follow-up study of 25 adult men, who have been operated by high resection of spermatic vessels during childhood (mean age 13 years). Results are very good: no testicular atrophy and in nearly all cases a normal sperm count or only slight OAT-syndrome. Compared with a group of non-treated men of the same age sperm counts are better and the number of fertile sperms higher. For that reason we recommend treatment as early as possible in childhood and puberty.