The modulatory effect of Tephrosia purpurea on benzoyl peroxide-induced cutaneous oxidative stress is described. Benzoyl peroxide is an effective cutaneous tumour promoter acting through the generation of oxidative stress. Benzoyl peroxide treatment increases cutaneous microsomal lipid peroxidation and hydrogen peroxide generation. The activity of cutaneous antioxidant enzymes, catalase glutathione peroxidase, glutathione reductase and glutathione S-transferase is decreased and the levels of cutaneous glutathione are depleted. Prophylactic treatment of mice with T. purpurea 12 h before benzoyl peroxide treatment resulted in the diminution of benzoyl peroxide-mediated damage. The susceptibility of cutaneous microsomal membrane to lipid peroxidation and hydrogen peroxide generation was significantly reduced (P < 0.05 and P < 0.001, respectively). In addition depleted levels of glutathione and inhibited activity of antioxidant enzymes were recovered to a significant level (P < 0.05). The protective effect of T. purpurea was dose-dependent. The results suggest that T. purpurea is an effective chemopreventive agent in skin that may suppress benzoyl peroxide-induced cutaneous toxicity.