A decrease in relative content of phospholipids and cholesterol simultaneously with increase in cholesterol esters and free fatty acids were detected in tissues of rat brain gray and white matters during autolysis at 37 degrees within 6-7 min, 1, 4 and 24 hrs; the most distinct alterations were observed in lipids of the gray matter especially at early (6-7 min) and late (24 hrs) stages of autolysis. In the gray matter, relative content of all the lipid fractions studied was restored to initial level within 4 hrs of incubation. In the white matter, during autolysis the content of cholesterol varied, the content of phospholipids was only slightly increased, while the level of free fatty acids was increased only at 24 hrs of incubation with synchronous decrease in content of triacylglycerols, cholesterol and, partially, phospholipids. These experimental data are of importance in resuscitation. Both common and dissimilar mechanisms of these lipid alterations are discussed. Not only the complex of hydrolase reactions but also that of transacylase and other reactions, involved in the degradation and biotransformation of brain lipids in autolysis, were noted.