The distributions of the N-methyl-D-aspartate (NMDA) receptor NR1, NR2A, NR2B and NR2C/D subunits were mapped in adult mouse cerebellum using subunit-specific antibodies. Immunostaining with anti-NR1 antibodies was prominent in cell bodies and dendritic arbors of Purkinje cells, was light to moderate in cerebellar granule cells, Golgi interneurons and interneurons in the molecular layer. Anti-NR2A subunit-specific antibody staining of mouse cerebellum was moderate in the granule cells, and moderate to dense in Purkinje neurons and Bergmann glia. However, Purkinje neurons were not immunolabelled in adult rat brain. Anti-NR2B subunit-specific immunostaining was prominent in Purkinje cell bodies and dendrites but absent from the granule cell layer. Anti-NR2C/D subunit-specific immunostaining was largely restricted to cerebellar granule cells. These studies reveal that NMDA receptor subunits display distinct but overlapping expression patterns in the adult mammalian cerebellum. Furthermore, we have observed some differences between rats and mice in terms of the NMDA receptor subunits expressed in specific cerebellar cell types.