Association of TNF gene polymorphism -308G>A with the development of nonalcoholic steatohepatitis in the Russian population was revealed. Carriers of allele A of the TNF gene marker -308G>A have significantly higher risk of nonalcoholic steatohepatitis development: OR=1.69 (1.05; 2.71). Allele A carriage by this marker predicts an increase in the basal HDL level and a decrease in LDL and IL-10 levels in the blood of healthy subjects. Patients with nonalcoholic steatohepatitis, differing by the TNF gene -308G>A marker genotype, differ by the time course of the markers of hepatocellular damage (ALT, AST), activity of hepatocyte apoptosis (tissue polypeptide-specific antigen), and activation of specific humoral immunity (γ-globulin) in response to therapy with ursodeoxycholic acid in a dose of 10-15 mg/kg over 4-6 weeks. Carriers of allele A of the TNF gene polymorphic marker -308G>A are more sensitive to ursodeoxycholic acid therapy than carriers of GG genotype.