The authors observed the joint effects of arsenic and lead on lipid peroxidation(LPO) in vitro and in vivo. In vitro, the authors used the extracted erythrocyte membrane of health adult men and divided them into three exposed groups. The first group was exposed to As2O3 (0, 0.4, 2.0 and 10.0 mmol/L). The second group was exposed to PbAc2 (0, 0.08, 0.4 and 2.0 mmol/L). The third group was exposed to As(10 mmol/L) + Pb (0.08 mmol/L). The results show that there is interaction between As and Pb on LPO of erythrocyte membrane. In vivo, the authors measured LPO levels of rat's plasma, blood glutathione(GSH) and superoxide dismutase(SOD) activity. By using 2 x 2 factorial design, Wistar rats were gavaged with As2O3 2.4 mg/(kg.d) and PbAc2 30 mg/(kg.d) as well as both arsenic and lead in water for 10 days. The results show that in the As-Pb treated rats, the levels of LPO did not change significantly, the GSH levels and SOD activity decreased significantly. The results of factorial analysis revealed a synergic effect of As-Pb on SOD activity.