We investigated the localization of major gangliosides in adult rat brain by an immunofluorescence technique with mouse monoclonal antibodies (MAbs). Five MAbs (GMB16, GMR17, GGR12, GMR5 and GMR13) that specifically recognize gangliosides GM1, GD1a, GD1b, GT1b and GQ1b, respectively, were used. We have found that there is a cell type-specific expression of the ganglioside in the rat central nervous system. In cerebellar cortex, GM1 was expressed in myelin and some glial cells. GD1a was detected exclusively in the molecular layer. GD1b and GQ1b were present restrictedly on the granular layer; GD1b was detected on the surface of the granular cell bodies, whereas GQ1b was present in the cerebellar glomerulus. GT1b was distributed intensely in both the molecular layer and the granular layer. In cerebral cortex, GM1 was detected in some glial cells. Dense staining was limited to the white matter. GD1a was distributed in layers I, II/III and Va, and the upper part of layer VI, whereas GQ1b was localized in layers IV and Vb, and the lower part of layer VI. GD1b was detected beneath layer III. GT1b appeared to be distributed throughout all layers. In other regions, such as hippocampal formation and spinal cord, the expression of the ganglioside was also highly localized to a specific cell type and layer.