Aim: To investigate the protective effects of prostaglandin E 1 (PGE 1 ) against H 2 O 2 -induced oxidative damage on human umbilical vein endothelial cells (HUVECs). Methods: HUVECs were pretreated with PGE 1 (0.25, 0.50, and 1.00 µmol/L) for 24 h and exposed to H 2 O 2 (200 µmol/L) for 12 h, and cell viability was measured by the MTT assay. LDH, NO, SOD, GSH-Px, MDA, ROS, and apoptotic percentage were determined. eNOS expression was measured by Western blotting and real-time PCR. Results: PGE 1 (0.25−1.00 µmol/L) was able to markedly restore the viability of HUVECs under oxidative stress, and scavenged intracellular reactive oxygen species induced by H 2 O 2 . PGE 1 also suppressed the production of lipid peroxides, such as MDA, restored the activities of endogenous antioxidants including SOD and GSH-Px, and inhibited cell apoptosis. In addition, PGE 1 significantly increased NO content, eNOS protein, and mRNA expression. Conclusion: PGE 1 effectively protected endothelial cells against oxidative stress induced by H 2 O 2 , an activity that might depend on the up-regulation of NO expression.