The state of antioxidant system and fatty acid composition of lipids in the liver tissues of rats of different sex at the ethanol and tetracycline action and at the influence of biologically active additives (BAA) "Alpha + Omega" at a dose of 0.5 mg/kg b.w. per os was investigated. It was found that the contet of lipid peroxidation products in the liver was increased at the action of 40% ethanol at a dose of 7 ml/kg b.w. per os and tetracycline--500 mg/kg and more profound at their joint using. However, the content of diene conjugates was stronger increased in the liver of females at the action of ethanol, while in the liver of males at the action of tetracycline (P < 0.05). It was shown that the application of the investigated compounds led to the reduction of an antioxidant defense system activity of males and females liver, as evidenced by the decrease of superoxide dismutase activity by 46 and 43% and reduction of glutathione content by 39 and 38% (P < 0.05). The activity of alanineaminotransferase, aspartateaminotransferase and alkalinephosphatase was increased in the liver of males and females under the influence of ethanol and tetracycline and more profound at their joint usage (P < 0.05). It was established that ethanol and tetracycline unidirectionally changed fatty acid composition of total lipids of rat liver, but at the ethanol action the changes were more expressed in females while at the tetracycline action in males. The application during 14 days of BAA "Alpha + Omega" to male and female rats with an acute tetracycline damage at subacute ethanol action led to partial normalization of prooxidant-antioxidant system and the relative content of total lipids fatty acids of the liver of both sexes animals.