Mutations in the dystrophin-glycoprotein complex cause muscle degeneration and dysfunctions in the central nervous system, including an impaired synaptic transmission in the outer plexiform layer (OPL) of the retina. To investigate the basis for this ocular phenotype, we analyzed the distribution of -dystroglycan, a central member of the dystrophinglycoprotein complex, in the chick retina by using the 43DAG/8D5 monoclonal antibody. This antibody reacted specifically with chick -dystroglycan, as indicated by its staining of the neuromuscular junction, and its reactivity with a single 43-kilodalton band in Western blots. In the retina, -dystroglycan was highly concentrated in the OPL and at the vitreal border of the retina, around the inner limiting membrane. Mechanically isolated and flat-mounted inner limiting membranes were stained by the anti--dystroglycan antibody, and this immunoreactivity could be extracted by detergent, indicating that -dystroglycan is associated with membranous structures bound to the basal lamina. Consistently, electron microscopy showed a concentration of -dystroglycan in the endfeet of Mu ¨ller glial cells exclusively in the region of direct contact to the inner limiting membrane. In the OPL, -dystroglycan immunoreactivity was concentrated in the distal extensions of rod and cone terminals protruding into the outer plexiform layer. There, -dystroglycan codistributed with the ␣ 1B subunit of the N-type voltage-gated calcium channel. By contrast to previous reports, we did not detect -dystroglycan directly associated with the synaptic regions of conventional or ribbon synapses of the retina. These results show that in the retina -dystroglycan is exclusively expressed by photoreceptors and glial cells and that -dystroglycan is highly concentrated in subcellular regions of glial cell endfeet and photoreceptor terminals. Moreover, the colocalization of -dystroglycan with N-type calcium channels in the outer plexiform layer indicates that both proteins might be part of a macromolecular complex.