A group of male rats were intoxicated within 24 h by three successive i.p. doses of ethyl alcohol (7.5 g per 1 kg of the body weight). In parallel, a control group of rats were dosed i.p. with a physiological saline. At time intervals of 0 h, 4 h, 24 h, and 48 h after the intoxication, the content of thiobarbiturate-reactive substances (TBARS) as product of lipid peroxidation within the liver and brain microsomes and mitochondria was followed. In liver microsomes of the experimental rats there was a rapid increase (by 220%) in the content of TBARS during 4 h after the last application of ethanol, later on the level of lipid peroxidation decreased to the low original value. In other organelles examined only an insignificant increase in the content of TBARS was found. The results prove that an acute intoxication by ethanol does elicit an oxidative stress of the organism, expressed by a transiently increased production of TBARS. These oxidative and harmful changes for the cell structures are mostly located in the liver microsomes but a rapid repair of this damage follows. However, if such a short-term excessive abuse of alcohol is repeated more often, the above changes may lead to severe alcoholic injury to the liver tissue.