Objective of the present study was to determine the effect of combined therapy with interferon alfa-2b (3 MU; thrice weekly s.c.) and ribavirin (1200 mg daily p.o.) on the number of copies of positive and negative strands of the hepatitis C virus RNA (HCV RNA) in patients with biopsy-proven chronic hepatitis C. Number of copies of both strands was determined by a TaqMan reverse transcription quantitative polymerase chain reaction (TaqMan RT Q-PCR) in the whole blood before treatment, and 4, 12 or 24 weeks after introduction of the treatment. Before the treatment positive strand of HCV RNA was more frequently detectable and its level was higher compared to that of the negative strand. In several patients, we observed therapy-induced transient appearance or increase in the number of copies of the negative HCV RNA strand. As a result of 24-week treatment, the negative strand of HCV RNA was eliminated from the blood more effectively than the positive strand. Our results suggest that the assessment of dynamics of changes of the positive and negative strands levels of HCV RNA in interferon-naive patients with chronic hepatitis C may be useful in monitoring short-term effectiveness of combined antiviral therapy. They also indicate that TaqMan RT Q-PCR appears to be a valuable tool in monitoring the therapy in these patients.