The antigenic expression of glial fibrillary acidic protein (GFAP), vimentin, S-100 protein and neurofilament triplex polypeptide was examined in cultured glial (Müller) cells from adult rabbit retina using immunocytochemical techniques. Most of the cultured cells were labelled with carbonic anhydrase C which has been considered to be the most specific marker of Müller cells. Most of the cultured cells were also positive for GFAP, a result which differs from previous observations on whole retina. Using a double labelling technique, 70-90% of cultured cells showed positive labelling for GFAP and vimentin although the staining intensity was stronger in the case of the latter. Fifty to seventy percent of cultured cells showed positive immunofluorescence to S-100 protein. Immunoelectron microscopy confirmed that GFAP and vimentin were localised along the intermediate glial filaments. S-100 protein was present in both the cytoplasm and the nucleoplasm of the majority of cells, but surprisingly in approximately 30% of cells the nucleoplasm was not labelled, a result which again is different from previously reported studies on whole retina. Neurofilament triplex polypeptide was not identified either by immunofluorescence or by immunoelectron microscopy. The results indicate that Müller cells in culture show a different antigenic expression to similar cells in whole retina.