Antioxidant activity of extracts from the submerged-liquid culture of mushrooms was measured using two systems : linoleic acid and mouse liver microsomes induced by various free radical sources. Mushrooms of Pleurotus ostreatus (Neutari), Phellinus linteus (Sanghwang), Paecilomyces japonicus (Dongchunghacho), Hericicum erinacium (Norugungdengyee) and Agaricus blazei (Shinryeong) in 1% mulberry tree powder-supplemented medium were incubated in a shaking incubator (200 rpm, $25^{circ}C$) for 3 days. Hot water extracts of mycelial cultures were freeze-dried, followed by fractioning with hexane, chloroform, ethylacetate and butanol in the order. Antioxidant activity of each sample was examined in free radical-induced linoleic acid oxidation in phosphate-buffered saline (PBS ) solution by measuring the amount of malonaldehyde (MA), and mouse liver microsomal systems by measuring the amount of thiobarbituric acid reactive substances (TBARS). In linoleic acid oxidation system, hot water extracts from the cultures of Pleurotus ostreatus, Phellinus linteus, and Paecilomyces japonicus exhibited stronger antioxidant activity than aqueous or butanol fraction and the combined fraction of hexane, chloroform and ethylacetate, but the hot water extract from Pleurotus ostreatus culture was the strongest activity. The antioxidant activity of the hot water extract from Pleurotus ostreatus culture was stronger than any other fractions in mouse microsomal system. These results suggest that hot water extract of Pleurotus ostreatus culture, and the cultures of Phellinus linteus and Paecilomyces japonicus could be useful for functional materials to reduce the oxidation of lipids in food systems induced by free radicals.