Abstract: Heavy metal toxicity causes impairment of variety of cellular process. Cellular failure to maintain balance between the generation and elimination of reactive molecules results in tissue damage. The purpose of this study was to determine the effects of Lead (BP) toxicity on Free Radicals (FR) production. Sixteen adult rats matched with age were randomly assigned to two groups, control and experimental. The experimental group was injected (IP) 1 mg kg-1 of body weight BP daily for seven days. Mean FR in the control group was 206.13±12.39 CARR U. In BP treated group the mean (±SEM) FR rose to 324.13±12.61 CARR U. The change in FR corresponds to 57% increase in the lead treated group. Thus, BP toxicity exposure mediates mitochondria damage and the subsequent oxidative stress. Based on the results of the present study, it can be concluded that BP toxicity causes elevation of Reactive Oxygen Species (ROS) which mediate inhibition of mitochondrial respiration in rats.