Abstract: Objective To investigate the effect of lead exposure on lipid peroxidation in pre school children.Methods Blood samples were collected from 408 subjects(217 boys and 191 girls)in five kindergartens.Blood lead levels (BLLs),activities of amino levulinic acid dehydratase(ALAD),supero xide dismutase(SOD)and glutath ione peroxidase (GSHPx),and contents of glutathione(GSH)in erythrocyte and levels of plasma malondia ldehyde(MDA)were measured.Results The BLLs of children showed significant differences among the five kindergartens.Children with BLLs>=100 g/L had significantly decreased erythrocyte ALAD activities and increased plasma MDA levels compared to the chil dren with BLLs<100 g/L.No significant change was observed in erythrocyte SOD and GSHPx activities,and GSH levels associated with elevated BLLs in the children.Conclusion ALAD and MDA may be the sensitive indicators of oxidative stress.