Interphotoreceptor matrix (IPM) proteins from a wide range of vertebrate species were examined by gel electrophoresis. Extensive similarities in the banding patterns of the proteins were found. S antigen, serum albumin and interphotoreceptor retinoid-binding protein (IRBP) were identified immunochemically. The latter two proteins dominate the IPM obtained from the apical surface of the retinal pigment epithelium, whereas IPM prepared from the retina washes contains IRBP plus outer-segment components including S antigen. IRBP is present in IPM from the all-cone lizard (Anolis) eye, as well as from rod- and cone-dominant animals. The ontogeny of IRBP in chick IPM is different from that of serum albumin in age of onset and rapidity of development. Comparison between Royal College of Surgeons rat IPM and normal rat IPM showed that several proteins are changed in amount. This study is a step toward a functional characterization of components common to the IPM of all vertebrates.