Serum FSH levels were significantly higher in infertile men with varicocele than in oligospermic and fertile men. Among the groups investigated there were no significant differences in serum LH, prolactin and testosterone levels. Men with varicocele and with severe depressed or absent spermatogenesis had a significantly higher serum FSH level than those with mild reduced or normal spermatogenesis. Leydig cell dysfunction was not detected in men with varicocele. Endocrine evaluation of infertile men with varicocele enables us to separate those who need not undergo surgical treatment (elevated serum FSH level) and those who need medical treatment after varicocelectomy (with disturbed Leydig cell function).