Anterior pituitary glands were homografted into the anterior chamber of the eye in female rats. The pituitary grafts survived and were well vascularized three weeks after the transplantation.The prolactin cells were morphologically active as shown by their well-developed Golgi complexes and granular endoplasmic reticulum and the exocytosis of secretory granules. The injection of dopamine into the common carotid artery of the graft-bearing rat rapidly suppressed the granule extrusion and then gradually induced a remarkable morphological atrophy in the prolactin cells.