Coenzyme Q10, a lipid soluble benzoquinone, has excellent antioxidant and membrane stabilizing properties in the cardiac tissue. The present study investigated the effects of coenzyme Q10 on in vitro LDL oxidation quantitavely. The formation of conjugated dienes, malondialdehyde (MDA) and electrophoretic mobility were monitored as markers of the oxidation of LDL, respectively. Coenzyme Q₁₀ showed a decrease the formation of conjugated dienes and MDA, respectively, against oxidation in vitro. Coenzyme Q₁₀ also reduced electrophoretic mobility of the oxidized human LDL. Thus, results showed that the coenzyme Q10 exhibits strong antioxidant activity in CuSO₄-mediated oxidation of LDL (P