Effects of Cadmium on purkinje Cell Density of Rat Cerebellum A lot of substance have been known to cause neuronal hyperactivity and cell death. Effects of cadmium on cerebral and cerebellar neurons are subject to interest for a long time which is present in cigarette smoke and filthy air. In present study, it was aimed to investigate the effects of cadmium sulphate (CdS04) on purkinje cells in Lobulus Simplex area in cerebellum of rats. CdS04 (0.0021mg/kg) is administered intracortically in 1.5 mm laterally of left Bregma with 1-2 mm depth. The same ratio of saline is administered to rats in control group. Seven-day group was treated for 7 days and animals in 30-day group received a 30 days treatment. Then, rats were perfused by neutral formaline intracardially. Cerebellum was separated from other structures of the brain and cut into sections with a distance 75-100 (m and with a thickness 6 pm. Sections were stained with thionin staining. Purkinje cells were counted under a light microscope with a magnification of 400x. Density of purkinje cells was found to be 18.79±0.16 neuron/mm in right cerebellum and 19.22+0.15 neuron/mm in left cerebellum of control group. In 7-day group, neuronal density was found to be 13.08±2.64 neuron/mm and 13.57+2.73 neuron/mm for right and left hemispheres, respectively. In 30-day treatment group, neuronal density was found to be 11.57+2.02 and 11.98±2.41 neuron/mm for right and left cerebellum, respectively. The difference between groups was statistically significant (p