PURPOSE: To characterize the site of expression of the α subunit of the receptor for ciliary neurotrophic factor (CNTFRα) in the retina of a variety of mammalian species, and determine whether CNTFRα is localized to photoreceptor cells. METHODS: The cellular distribution of CNTFRα (protein) was examined by immunocytochemistry in the adult retinas of several mammalian species that included mouse, rat, dog, cat, sheep, pig, horse, monkey, and human. Developing retinas from 3-day-old and 6-day-old rats were also included in this study. The molecular weight of CNTFRα in rat, dog, cat, pig, and human retinas was determined by immunoblotting. RESULTS: CNTFRα immunolabeling was present in the retina of all species. A common pattern was observed in all species, and represented labeling of the nerve fiber layer (NFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), and outer plexiform layer (OPL). CNTFRα did not immunolocalize to photoreceptor cells in both adult and developing rodent retinas, but was consistently observed in both rods and cones of non-rodent species. The molecular weight of CNTFRα in mammalian retinas was approximately 61-64 kDa. CONCLUSIONS: These findings highlight a significant difference in the expression of CNTFRα in the retina of rodent and non-rodent mammalian species. The expression of CNTFRα by rods and cones in non-rodent species may suggest a direct mechanism of action if CNTF administration results in photoreceptor rescue.