The present investigators after studying 160 biopsies of the cryptorchid testis in 148 children, find that in 15% of the testes there is an absence of germinative elements, in 45% a considerable diminution of spermatogonia and in 2 cases an anorchidism. The finding of a diminution of diameter of the seminiferous tubules confirms the work of other investigators. The problem of a testicular dysgenesis as the cause of cryptorchidism is discussed. Testicular biopsies during surgical treatment are essential in order to give a prognosis, taking into account the present knowledge of the evolution of these lesions.