As compared to a control group, the study of the pituitary reserve of gonadotrophins in 50, not yet puberous, cryptorchid boys, evoked that there is a heterogeneity in cryptorchism. The LH pituitary reserve may be insufficient, normal or increased; the FSH pituitary reserve may be normal or above normal. A longitudinal study of these patients, as well as the correlations with ultra-structural and histologic studies should lead to a better understanding of the significance of the hormonal abnormalities encountered in cryptorchism, and to a better appreciation of the associated testicular changes.