The aim of this research was to define the influence of long-term ethanol intoxication on the changes in end products of lipid peroxidation, reacting with thiobarbituric acid (TBA-reactive products) and free SH-groups concentrations in rat brains. The experiment was conducted on male Lewis rats. The experimental groups received a 1-molar ethanol solution and the control group received tap water. The animals were killed after 4, 8 and 12 weeks of intoxication and their brains were collected for further examination, encompassing measurement of the concentration of TBA-reactive products and free SH-groups. A statistically significant increase in the concentration of TBA-reactive products in 4th week of intoxication and decrease in the concentration of free SH-groups in 8th and 12th week of intoxication--compared to the control group--was noticed.