The objective of this study was to investigate the antioxidative capacity of oregano extracts. Amount of oregano extract at which DPPH radical scavenging activity was inhibited by 50% was $21.8{mu}g$ as compared to 100% by pyrogallol as a reference. Total antioxidant status was examined by total antioxidant capacity against potent free radical reactions. Total antioxidant capacities of oregano extract at the amounts of 7.5 and $15{mu}g$ were 15.1 and 31.4 nmol Trolox equivalents, respectively. Oxygen radical absorbance capacities of oregano extract at the amounts of 0.2 and $0.4{mu}g$ were 1.4 and 2.4 nmol gallic acid equivalents, respectively. Total phenolic contents of oregano extract at the amounts of 30 and $75{mu}g$ were 40.5 and 83.9 nmol gallic acid equivalents, respectively. The inhibitory effect of oregano extract on lipid peroxidation was examined using rat liver mitochondria induced by $FeSO_4$/ascorbic acid. Oregano extracts at the amounts of 20 and $50{mu}g$ decreased TBARS level by 20 and 64%, respectively. Thus strong antioxidant effects of oregano extract seem to be due to, at least in part, the prevention against free radicals-induced oxidation, followed by inhibition of lipid peroxidation.