It has been suggested that low circulating levels of androgens and gonadotropins found in impubertal subjects is due to a low -- setted feed-back regulation system, i.e. sensitivity of that system is higher than that of adult subjects. Cultures of adenohypophysial tissue of 2 to 6 days old male rats were performed and gonadotropins release compared to that obtained from similarly conducted adult male rats pituitary cultures (previous paper). Newborn rat hypophysis was more sensitive to factors stimulating LH release (LH-RH) and FSH release (testosterone). In contrast, testosterone inhibition of gonadotropins response to LH-RH was similar to that of adult tissue. Since trophic factors influence could not be totally excluded, it was concluded that pituitary tissue does not show marked variation of sensitivity with age.