We previously described the differential distribution of major gangliosides (GM1, GD1a, GD1b, GT1b and GQ1b) in adult rat brain detected by specific antibodies (Kotani, M., Kawashima, I., Ozawa, I., Terashima, T. and Tai, T. Glycobiology, 3, 137-146, 1993). We report here the distribution of minor gangliosides in the adult rat brain by an immunofluorescence technique with mouse monoclonal antibodies (MAbs). Ten MAbs (GMR6, GMB28, GMR11, GMR19, GMR2, GMR7, GGR51, AMR10, NGR54 and NGR53) that specifically recognize GM3, GM2, GT1a, GD3, O-Acdisialoganglioside, GD2, GM1b, GM4, IV3NeuAc alpha-nLc4Cer and IV6NeuAc alpha-nLc4Cer, respectively, were used. Our study revealed that there is a cell type-specific expression of minor gangliosides, as well as major gangliosides, in the rat brain. In the cerebellar cortex, GM3 was expressed intensely in the white matter and slightly in the granular layer. GD3 was present in both the granular layer and the white matter, but not in the Purkinje cell layer or in the molecular layer. An O-Ac-disialoganglioside, which was suggested to be O-Ac-LD1, was detected exclusively in both the molecular layer and Purkinje cell layer. The presence of GD2 was restricted to the granular layer. GM4 was associated with some astrocytes, but not with myelin or oligodendrocytes. GM2, GT1a, GM1b, IV3NeuAc alpha-nLc4Cer and IV6NeuAc alpha-nLc4Cer gangliosides were not clearly detected in the cerebellar cortex. In other regions, such as cerebral cortex, hippocampal formation and spinal cord, the expression of the gangliosides was also highly localized to a specific cell type and layer.