150 adult patients were assigned pegylated interferon alpha-2b (once weekly 1.5 microg/kg) plus ribavirin (800-1200 mg depending on bodyweight). The treatment lasted 52 weeks and was completed by 139 persons (92.7%). Because of adverse events the treatment was interrupted in 7 persons, 4 other persons resigned. Periodical reduction of pegylated interferon doses was necessary in 19% and the reduction of ribavirin in 21% of patients. Six months after the completion of treatment HCV-RNA was negative in 82 (59%) patients. Neither hepatitis C virus genotype, nor viremia was marked in the study. The negative correlation between the degree of fibrosis in the liver tissue and the results of sustained virological response was stated. Degree of inflammation at liver tissue, sex, age over and less than 40 years did not correlate with the final virological results. The recurrence of infection happened at 7% of the treated persons (negative HCV-RNA directly after the treatment--positive 6 months after the completion). During the treatment period, and comparison with the results obtained before its implementation, statistically significantly decreased: hemoglobin concentration, the number of leukocytes, granulocytes and thrombocytes. They returned to the referential values half a year after the completion of treatment. The activity of enzymes (AIAT, AspAT, GGTP) was decreasing statistically significantly since the first weeks of the treatment till the end and remained significantly lower after 6 months. In both sexes statistically significant reduction of bodyweight was stated, while it increased during the six months after the completion of treatment. Adverse events, which mostly were mild and were not the cause of interruption of treatment, were numerous and occurred at different frequency, in the range from over 50% (flu-like) to 0.7%.