ABSTRACT. Hypogonadotrophic hypogonadism was suspected in three male newborns on the basis of a very small penis associated with cryptorchidism and a positive familial history of Kallmann's syndrome in one, of isolated anosmia in the two others. It was demonstrated in early infancy by the lack of postnatal rise of LH and testosterone, and by a blunted response to LHRH and HCG stimulation tests. These data suggest that the postnatal follow‐up of plasma LH and testosterone allows the diagnosis of hypogonadotrophic hypogonadism in male infants with micropenis and cryptorchidism and that careful familial investigation may be useful in these cases.