Three genetically distinct isozymes of the catalytic subunit of the Na,K-ATPase have been detected and have been designated α1, α2, and α3. To determine whether their expression is restricted to identifiable neurons and glia, specific monoclonal antibodies were used for immunofluorescent localization in the rat retina and optic nerve. The patterns of staining were markedly different, suggesting differences in cellular localization. Photoreceptor inner segments and optic nerve fibers expressed predominantly α3. Müller glia in the retina and astrocytes in the optic nerve expressed α1 and α2. Isolated, dissociated bipolar, horizontal, and Müller cells expressed different isozymes separately or in combination. The complexity of staining of neurons and their axons and dendrites suggested that Na,K-ATPase isozyme expression is not stereotyped, but is tailored to the ion transport needs of individual cell types, and targeted to specified membrane domains.