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Purpose: To investigate the effect of low level cadmium (Cd) exposure on the activity of superoxide dismutase (SOD) in rat. Methods: Thirty-two male albino rats were divided into four groups of eight animals each. Group one received distilled water and served as control. The other three groups were exposed to 100, 200 and 300 ppm cadmium doses, respectively, in their drinking water for 6 weeks. At the end of 6 weeks, blood, brain and liver were removed from the animals and SOD activities were investigated spectrophotometrically at 480 nm. Results: The data revealed a significant (p < 0.05) decrease in organ weight of the exposed rats, and with the highest cadmium accumulation in liver ranging from 2.99 ± 0.20 μg Cd/g tissue in control to 34.57 ± 2.06 μg Cd/g tissue for the 300 ppm dose group. Exposure to cadmium resulted in significant (p < 0.05) decrease in SOD activity in plasma, erythrocytes, brain and liver in a dose-dependent manner compared to control. The data showed a negative correlation between tissue cadmium and SOD in plasma, erythrocyte and brain. While positive associations were observed between blood and tissue (brain and liver) cadmium and SOD, a significant (p < 0.01), negative correlation was found between tissue cadmium and SOD. Conclusion: As Cd dose increase, plasma, erythrocyte, brain and liver SOD activities decrease. This might affect the maintenance of the normal body physiological conditions. Keywords: Cadmium, Superoxide dismutase, Liver, Brain, Toxicity, Environmental contaminant