The author studied the influence of vitamin D on the sexual function of albino rats. An administration of vitamin D to the castrated animal prevents the atrophy of the uterus to a considerable degree. Administration of an optimal dose of vitamin D accelerates the growth of ovarian follicles and uterus of noncastrated young and adult animals, on the contrary, an excess of vitamin D, especially when administered for a long period, restrains and suspends the sexual function of the animal. Young animals administered with a large dose of vitamin D show the temporary acceleration of sexual function, but the successive administration of an excess-dose causes the disorder of sexual function prior to that of general conditions. In general the effect of administration of vitamin D to the young animals is more prominent than that to the adult ones. The action of estrogen is enhanced by the simultaneous administration of an adequate dose of vitamin D, but it is reduced by a large dose.