AIM: To explore the effect of oxides of low density lipoprotein (OX - LDL)on apoptosis in vas- cular endothelial cells(EC) and its possible mechanisms. METHODS: Culted vascular ECS were incubated with OX - LDL(0.1?g/L or 0. 3?g/L) for 4 hours, flow cytometer with PI staining methed was used to determine the rate of cellular apoptosis, gel - electrophoresis was performed to observe foe DNA ladder of apoptosis, cellular RNA was isolated and reverse transcription-polymerase chain reaction (RT - PCR)was performed to determine Fas antigen ex- pression. RESULTS:OX - LDL treatment induced apoptosis in EC dose - dependently. No DNA ladder was ob- served in control EC. But it presented in EC beated with low dose of OX - LDL, and was even more when beted with higher dose of OX - LDL. RT - PCR revealed Fas antigen baldly had any expression in basic condition, OX - LDL treatment induced Fas antigen in EC in a dose dependent manner. CONCLUSION: OX - LDL can induce apoptosis in EC, upregulaton of Fas antigen expression maybe one of the possible mechanisms.