Aqueous extract of Dracocephalum tanguticum Maxim. (DtM ),when given ig or ip to experimental hypoxia mice,markedly increased their tolerance to normobaric and hypobaric hypoxia. Erythrocyte superoxide dismutasc (SOD ) activity of mice or rats determined at high altitude (animaquing mountain 4700 m above sea level ) showed an elevated dismutation activity of peroxide anions. At an experimentally simulatcd altitude of 6000 m above sea level,determunation of MDA, Hb and Hct showed an obvious reduction of all the abnormally elevated criteria. It is suggested that the antihypoxia activity of DTM may be partly due to its free radical scavenging activity