The effects of different concentrations of alpha-tocopherol and beta-carotene on low density lipoprotein(LDL) oxidation were examined. LDL was oxidized by Cu2+ in a cell-free(10 mumol/L Cu2+ in PBS) system. The results showed that alpha-tocopherol and beta-carotene inhibited the oxidative modification of LDL in this system as evidenced by a concentration-dependent decrease in lipid peroxide(thiobarbituric-acid-reasting substances activity, TBARS) and the electrophoretic mobility of LDL. The effect of alpha-tocopherol on the generation of TBARS was stronger, while on the electrophoretic mobility was weaker than that of beta-carotene. Both alpha-tocopherol and beta-carotene slightly but not significantly reduced lipofusin. It suggested that the mechanisms were different. Thus, beta-carotene, as well as alpha-tocopherol, inhibit LDL oxidation and might play important roles in reducing the generation of oxidized LDL.