Abstract The subcellular distributions of the γ- and βII-subspecies of protein kinase C (γ- and βII-PKC) were studied in the rat hippocampus by light and electron microscopic immunocytochemistry. Both subspecies were abundant in the hippocampus with distinct subcellular distributions. The immunoreactivity of γ-PKC was observed throughout the Ammon's horn, while intense βII-PKC immunoreactivity was observed predominantly in the CA1 region. γ-PKC was distributed diffusely through the cytoplasm of pyramidal cells from the perikarya to the dendritic spines. In contrast, βII-PKC was concentrated around the Golgi complex and present diffusely in distal dendrites, except for the dendritic spines. Neither PKC subspecies could be detected in the presynaptic terminal. The postsynaptic localization of γ- and βII-PKC in CA1 suggests that both PKC subspecies may correlate to long-term potentiation in the CA1 region contributing to the postsynaptic side. γ-PKC may have a specific function not only in CA1 but also in the mossy fiber-CA3 pathway at the postsynaptic side. βII-PKC may have another function concerning the Golgi complex in CA1.