Presumed GABA neurons were studied in chick, guinea pig, and rabbit retinae with an immunohistochemical procedure aimed at direct demonstration of the endogenous GABA. In all species, a subset of amacrine cells was immunoreactive, as well as numerous fibers in the inner plexiform layer. In the chick, immunoreactivity was also demonstrated in horizontal cells, and single cell processes could be distinguished in both plexiform layers. The study indicates that the endogenous stores of GABA in GABAergic neurons can be visualized with immunohistochemical techniques. This direct approach thus gives additional information and probably is less subject to nonspecific staining than the demonstration of enzymes linked to GABA synthesis and metabolism. It also gives superior resolution in comparison with the autoradiographic techniques currently used for demonstrating GABA neurons. Invest Ophthalmol Vis Sci 27:674-678, 1986.