AIM:To study the effect of adiponectin (APN) on lipid peroxidation in human umbilical vein endothelial cells (HUVECs) induced by hydrogen peroxide (H2O2) in vitro. METHODS:The effect of H2O2 on apoptosis was measured by flow cytometry with Annexin V-FITC labeling. The concentration of malonaldehyde (MDA) in HUVECs was detected by thiobarbituric acid (TBA) method. The activities of superoxide dismutase (SOD) and catalase (CAT) were measured by colorimetric assay. The scavenging rate on superoxide anion radicals in xanthine oxidase system and OH radicals produced by Fenton reaction were also tested. RESULTS:APN significantly inhibited H2O2-induced apoptosis. H2O2 increased MDA production and reduced the activities of SOD and CAT,which were inhibited by APN. APN did not alter the activities of SOD and CAT in normal condition. APN dose-dependently decreased the superoxide anion radicals,with the scavenging rate of 11.9%,21.4%,36.9%,respectively,and scavenged OH radicals. CONCLUSION:APN inhibits apoptosis and protects endothelial cells against lipid peroxidation insult by scavenging the free radicals.