Abstract: Background and Objective: The effect of lead on several metabolic reactions in the radish plant has been investigated. The present study was conducted to evaluate the potential role of enzymes activity, their isoenzyme profile pattern and free radical formation as biomarkers of Pb pollution in the radish (Raphanus sativus L.) plant. Materials and Methods: Varied concentrations of Pb(NO3)2 ranging from 25-500 ppm in the growth media were used. The plant samples were collected after 40 days growth period. Lead and micronutrients concentration, the profile of electron spins resonance determination and hydrolytic enzymes activities were analyzed. Results: Lead concentrations in roots and leaves increased with increasing Pb concentration in the tested media; however the most accumulation were observed in leaves. Generally, the concentration of micronutrients such as Fe, Zn, Mn and Cu declined in leaves compared to the roots. Results of the profile of Electron Spin Resonance (ESR) determination showed a decrease in unstable free radical level in the roots, followed by a significant increase with increasing Pb concentrations. The Pb induced changes in some enzymes activity and its isoenzyme profiles such as acid phosphatase (AP), esterase (EST) and polyphenol oxidase (PPO) in leaves and roots of radish plant. Results of isoenzymes suggested that the staining intensities of isoform patterns were consistent with the changes of the activities assayed in solutions. Conclusion: These results suggested that (Raphanus sativus L.) seedlings may have a better protection against oxidative stress by increasing antioxidant enzymes activity exposed to Pb toxicity.