The rate of free-radical oxidation in the blood of patients with hereditary motor-sensor neuropathies (HMSN) and myotonic dystrophy (MD) type I was evaluated by the generation of active oxygen forms, the content of the products of lipid peroxidation and the total blood antioxidant activity. The change in the generation of active oxygen forms was characterized by the increase in the spontaneous blood chemiluminescence in patients with HMSN compared to controls. In patients with MD, the concentration of the products reacted with thiobarbituric acid was identified. In most cases, no correlations between the parameters studied and clinical/genetic characteristics were found. This fact suggests that the changes are individual and the prescription of drugs with antioxidant activity to patients with HMSN and MD should be substantiated.