Blinding adult male hamsters either by bilateral orbital enucleation or by surgical removal of the inner retinal layers (ganglion cell layer, bipolar cell layer and rod cells) caused atrophy of the testes, seminal vesicles and coagulating gland and also led to a significant reduction in the levels of immunoreactive luteinizing hormone (LH) and prolactin in the anterior pituitary glands. Pinealectomy, superior cervical ganglionectomy or decentralization of the superior cervical ganglia negated the depressant effect of light deprivation on the growth of the reproductive organs and on pituitary LH levels. The surgical procedures also returned pituitary prolactin levels toward those in intact controls but the levels of this hormone still remained somewhat below normal. The results indicate that the pineal gland in the light-deprived male hamster restricts either the synthesis or the release of LRF and prolactin-inhibiting factor within the hypothalamus.