This study was performed to determine the effects of antimutagenicity from Barley (Hordeum vulgare). In Salmonella typhimurium reversion assay (In vitro test), the extract of Barley (Hordeum vulgare) inhibited mutagenic activity of 4-NQO and Trp-p-1 with 59 mix. in Salmonella typhimurium TA98 and TA100. In Micronucleus test (In vivo test), the methanol extract of Barley (Hordeum vulgare) inhibited micronucleus formation in bone marrow by cyclophosphamide. The $eta$-glucan of Barley (Hordeum vulgare) showed inhibitory effects of 59-77% in mutagenic activity of 4-NQO by Salmonella typhimurium TA100. The mutagenicity of Trp-p-1 with S9 mix. by Salmonella typhimurium TA98 showed inhibitory effects of 24-56%. The methanl extract (M) was fractionated with ether (MI), ethylacetate (M2), buthanol (M3) and water (M4). The Antimutagenicity of Trp-p-1 with 59 mix. by Salmonella typhimurium TA98 in Barley fraction showed the following: methanol extract (99.58%)>ether fraction (98.05%)>buthanol fraction (56.90%)>water fraction (56.72%)>ethyl acetate fraction (28.72%). Among them, ether fraction in TA 98 showed strong antimutagenicity effects (85.56%, 98.05%) against mutation induced by 4-NQO and Trp-p-1. As concentration of the methanol extract increased (1.25~5 g/kg/10 cc), micronucleus formation in bone marrow by chemical mutagen (CP) showed inhibitory effects of 50% (p< 0.05).