The localisation and immunochemical identification of 3 different forms of protein kinase C (PKC-α, PKC-β and PKC-γ) in retinas of different species were analysed by immunohistochemistry and SDS-PAGE-Western blotting, respectively. Only in some cases was there a correlation between the findings from each procedure. One reason for the lack of correlation could be the small amounts of PKC present in some retinas, which made detection possible only by first concentrating the antigen by SDS-PAGE and then carrying out Western blotting. Another possible reason is that an antibody recognises unknown antigens immunohistochemically, but, because of their specific characteristics, they are denatured when subjected to SDS-PAGE and Western blotting and therefore remain undetected. PKC-β immunoreactivity is present in rabbit, frog and goldfish retinas but absent from the rat retina. However, SDS-PAGE and Western blotting experiments showed that the PKC-β isoenzyme is absent from the fish retina but present in the rat retina. PKC-β immunoreactivity in rabbit retina is present in ganglion and/or amacrine cells; in the frog retina the enzyme is associated with some bipolar cells. In the goldfish retina, PKC-β is associated with a large population of cells in the ganglion cell layer as well as with some amacrine cell bodies. PKC-α is present primarily in bipolar cells of rat, fish and rabbit retinas and was not detected by immunohistochemistry or blotting experiments in the frog retina. SDS-PAGE and Western blotting of retinal extracts from different species showed that PKC-γ occurs in the rabbit where it was associated with ganglion and/or amacrine cells. While PKC-γ could be detected by blotting experiments in brain extracts from frog, rat and rabbit it was absent from both retina and brain extracts of the goldfish and frog and rat retinal extracts. However, PKC-γ immunoreactivity was associated with many amacrine cells in the frog retina as well as ganglion-like cells in the fish retina.