We measured serum type III procollagen peptide, type IV collagen (IV-C), and hyaluronan (HA) in 36 hemophiliacs with hepatitis C virus (HCV)-related chronic liver disease. We also measured these markers in 19 interferon (IFN)-treated patients before and after a 6-month course of IFN-alpha. The serum concentrations of IV-C and HA were correlated with the stage of fibrosis (IV-C r = 0.38; HA r = 0.78). These markers fell only in complete responders showing sustained clearance of serum HCV RNA by IFN. These results suggest that, in hemophiliacs with chronic liver disease, serum HA measurement might be an alternative to liver biopsy and reflect the response to IFN.