GOMORI (1950) has described an elastic tissue stain which also stains specifically certain of the “basophil” cells of the rat pituitary. Halmi, (1950) investigated the responses of the Gomori staining “basophils” to specific endocrine deficiencies. Purves and Griesbach (1951a) reported that the cells stained specifically by the Gomori stain in the rat pituitary corresponded with those “basophils” to which a thyrotrophic function has been ascribed (1951b). The evidence for the thyrotrophic function of this group of “basophils” was obtained in experiments correlating the glycoprotein content of the “basophil” cells as revealed by the staining method of McManus (1946) with the hormone content of the gland under conditions of specific endocrine stimulation or depression. In this publication evidence of the identity of the Gomori staining granules with the glyco-prctein granules revealed by the McManus technique is presented. The functional responses of the Gomori staining granules to conditions affecting the thyroxine supply have been investigated.