In the retina, the membranous outer segments shed from the photoreceptors are phagocytized by the adjacent retinal pigment epithelial cells. These cells are some of the most active phagocytic cells in the body and like photoreceptors must survive the lifetime of the organism. The initiation of engulfment by the pigment epithelial cells occurs by an unidentified mechanism. The ingestion of particles by many, but not all phagocytic cells, is mediated by Fc and C3 receptors located on the external plasma membrane. The present experiment reports our unsuccessful attempt to demonstrate either the Fc or C3b receptor on the plasma membrane of RCS rat pigment epithelial cells.