Abstract: The physiological function of cerebellum declines during ageing, but its neural mechanism is not still clear. Therefore, we applied an immunohistochemical method to exhibit the Glu and GABA immunoreactive (Glu-IR and GABA-IR) cells, to investigate aged changes of Glu/GABA expression in the cerebellar cortex of young adult and old cats, and to discuss the possible impact of these changes. Under the Olympus BX-51 light microscope, the density of the immunoreactive cells and its gray value in the molecular layer, Purkinje layer and granular layer were counted respectively with Image-Pro Express Software 5.1. Compared with young cats, the density and average grey value of Glu immunoreactive cells increased significantly in the Purkinje and granular layer of old cats (P﹤0.01). The density and intensity of GABA immunoreactive neurons declined significantly in the molecular and Purkinje layers of old cats (P﹤0.01). The density of GABA immunoreactive neurons showed no evident differences in the granular layer between young and old cats (P﹥0.05), but the intensity of GABA immunoreactive neurons was visibly weaker in the granular layer of old cats (P﹤0.01). The results indicated that changes of Glu/GABA expression in the cerebellar cortex during ageing may be one of the important factors mediating the functional degeneration of accurate timing and neurons lost in old individuals.