The aim of our study was analysis of relation between HLA class II antigens and the liver disease severity in chronic hepatitis C (CHC) patients. The subject of analysis was data obtained from 134 CHC patients with disease confirmed by histopathologic test (F/M: 62/72; age 16-74; average age 41.4 +/- 12.7 yrs), HCV RNA-positive, HbsAg- and HIV-negative with no coexistence of any other liver diseases. Liver biopsy specimens were estimated according to Ishak's criterions (grading 0-18; staging 0-6). HLA DRB1 alleles were determined by a commercial method INNOLiPA DRB (Innogenetics, Belgium). Statistical analysis considered alleles occurring with frequency higher than 10%. The necroinflammatory activity (average grading score) was compared in groups of patients with- and without particular allele. The frequency of each allele's occurrence was analyzed according to patients sex, age and staging score of liver fibrosis. In statistical analysis t-Student test and chi-squared test with or without Yates' correction were applied. Statistically significant correlation was found between occurrence of DRB1*13 and DRB1*07 alleles and necroinflammatory activity intensification, and between occurrence of DRB1*13 allele and progression of liver disease. Mild liver damage, instead, expresses statistically significant relation with DRB1*11 allele.