One hundred and twenty-five children with cerebral palsy (n = 108) and organic CNS lesions (n = 17) have been studied. A control group included 30 children without any neurological lesions. Lipids and phospholipids spectra, Ca, Mg- and Na, K-ATPases, intensity of red blood cells lipid peroxidation and erythrocyte free magnesium content have been determined. Children with cerebral palsy had a higher percentage of cholesterol ethers and final products of lipid peroxidation in red blood cells--Shiff bases and a decrease of intraerythrocytic free magnesium. Patients with atonic-astatic syndrome were characterized by a sharp increase of Na, K-ATPase activity accompanied by increased content of such phospholipids as cardiolipin and phosphatide acid as well as Shiff bases. In patients with organic CNS lesions, Shiff bases content was similar to that in the control group, intracellular magnesium also did not differ significantly from the controls, but cardiolipin, phosphatide acid, cholesterol ethers and triglycerol concentrations were reduced. All the patients with neurological disorders had an increased percentage of phosphatidilcholin in red blood cells.