The aim was to study the hematological side effects of Peginterferon alfa-2a (Pegasys) and Ribavirin (Copegus) therapy in chronic hapatitis C. 46 patients with chronic hepatitis C treated with 180 microg/week Pegasys s.c. + 1000-1200mg/day Copegus, were monitored monthly regarding the leucocyte, thrombocyte and erythrocyte number, the level of total and unconjugated bilirubinaemia. Leucopenia under 4000/mmc was found at 39,13% of the patients, at 4,34% leucopenia was under 2000/mm3. Thrombocitopenia under 100000/mm3 was found at 30,43%, at 8,69% it was under 80000/mm3. Anaemia was found at 17,39% of the patients. Because of the side effects, at 4,34% of the patients it was necessary to reduce the dose or temporarily stop the therapy. Haemolytic anaemia, caused by Ribavirin was present at 8,69% of the cases and was solved by reducing of the dose. Under the antiviral therapy with Pegasys and Copegus, leucopenia and thrombocytopenia are frequently present, anaemia isn’t so frequent – but it’s well – tolerated by the majority of patients and only some cases needed a reduction of dose or discontinuation of the therapy.