A patient with Beckwitt-Wiedemann's syndrome is described in which associated malformations were hemihypertrophy of the body, medullary sponge kidneys and absence of testes and internal ducts. On the other hand, we demonstrated biochemically the existence of testosterone secretion, with active response to a 3-day HCG stimulation as well as prepuberty levels LH and FSH. This demonstrated the existence of functioning Leydig's cells. The diagnosis of agonadism and anorchia could not be entirely true since they lead to an erroneous conclusion that there always are some disseminated Leydig's cells.