Six-hour accumulations of 125I were measured in the growing oocytes and thyroids of laying Japanese quail injected with 0.002 to 2 mg. of FSH or 0.004 to 4 I.U. of TSH per day for six days. FSH at 0.2 and 2 mg./day increased the 125I content of the growing oocytes to 1.4 times the control values. The numbers and the total weights of these growing oocytes doubled. The egg-laying rate remained unchanged. The FSH-induced apparent stimulation of 125 I transference was seen as a consequence of the increase in oocyte material rather than to a direct effect of FSH on the membranes of the avarian follicular cells. TSH did not increase the transference of 125I.