Extirpation of the pineal gland in rats causes acceleration of sexual maturation. This effect can be prevented by grafting the pineal into the anterior chamber of the eye at the time of pinealectomy. Evidence of accelerated sexual maturation was seen in the gonadal weight, histological appearance and total P content. The adrenal ascorbic acid was depressed in pinealectomized animals. The authors suggest the pineal exerts a hormonal suppressing or antagonistic effect upon the adenohypophysis.