After transplantation to the anterior eye chamber of hypophysectomized or intact male hosts, neonatal rat pituitary glands exhibited evidence of TSH secretion only. Pars intermedia had no effect on adenohypophyseal function and was without detectable effect when grafted alone. TSH concentration of ocular grafts was similar to that of normal glands; unlike normal glands, however, it was not depleted by PTU feeding and did not rebound to supranormal levels after PTU withdrawal. Hypophysectomized test animals were injected with TSH from ocular grafts and that from normal glands over a range of 2–300 mu./day. TSH from both sources produced qualitatively and quantitatively similar effects on thyroid weight and T/S ratio. The results are discussed with respect to neural control of TSH and the hypothesis of separate growth and metabolic TSH principles.