Abstract: Hydrogen peroxide(H₂O₂)-induced cell dimage and Ca²⁺ influx into bovine aorticendothelial cells (BAEC) were investigated.Our data suggested that H₂O₂ could dose-and time-dependently induce damage in cultured BAEC assessed by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide(MTT) assay and increase malondialdehyde (MDA) production,which reflects the level of lipid peroxidation. Exposure of BAEC to H₂O₂(100 μmol·L^-1) caused significant increase in intracellular free calcium(Ca²⁺i) within 6 min,suggesting that the increase ofCa²⁺i might implicate in H₂O₂-induced cell damage. The calcium inhibitor nifedipine was found to dose-dependently decrease the increase of Ca²⁺i caused by H₂O₂ and protect BAEC against H₂O₂ -induced damage reflected by significant decrease of MDA production and increase of MTT value. These results indicate that overload of calcium might be responsible to some extent causing oxidative damage to cells.