The effect of a local exposure of rat heads to X-ray radiation at a dose of 200 Gy on the number of phospho- lipids and neutral lipids in the nuclear fraction ofneocortex neurons and glia has been investigated A decrease in the amount ofphosphatidylinositol and an increase in sphingomyelin in neuronal nuclei occurred 2 h after irradiation at the time of repair of locomotive disorders. The amount of phosphatidylcholine and phosphati- dylinositol dropped, and the amount of sphingomyelin and cholesterol increased in the nuclei ofglial cells of the neocortex. Sphingomyelin, phosphatidylinositol, phosphatidylcholine and cholesterol of neuronal nuclei are involved in the dynamics of the CNS syndrome in mammals. Radio resistance of the responses of lipid nuclei in mammals with the CNS syndrome has been shown and a possible role of lipids in the post-irradia- tion DNA repair has been suggested.