Dose dependent study was performed to identify subcritical level of Pb and Cd. Blood delta-ALAD activity was inhibited by (0.1 mg/kg body wt) of both lead and cadmium in isolation and combination, the extent of which increases with duration of exposure. Hepatic delta-ALAD activity however is less affected by Cd and Pb-Cd together than Pb alone. Erythrocyte acetylcholinesterase activity though decrease in all groups, is not significant.