BACKGROUND/AIMS We investigated the clinical application of serum fibrosis markers in a long-term follow-up of patients with chronic hepatitis C treated with interferon-alpha. METHODOLOGY This study included 52 patients treated with interferon-alpha (total: 480 MU) for 6 months. They each underwent liver biopsy before and after treatment. Twenty-eight patients who underwent liver biopsy less than 2 years after treatment were classified as group 1, and 24 patients as group 2. The two groups were subdivided into HCV RNA-negative responders and HCV RNA-positive nonresponders. Liver specimens were estimated using grading and staging scores. Serum hyaluronan, PIIIP, and type IV collagen levels were measured before and after treatment. RESULTS In the responders of groups 1 and 2, grading score after treatment was significantly decreased compared with that before treatment. Staging score after treatment was significantly improved only in the responders of group 2. In the responders of group 2, serum hyaluronan level was significantly decreased compared with that before treatment. In group 2, the grading score was significantly correlated with serum PIIIP and type IV collagen levels, and the staging score was significantly correlated with only serum hyaluronan level. CONCLUSIONS These findings indicate that the serum PIIIP and type IV collagen levels reflect the activity, and serum hyaluronan reflects the degree of fibrosis in liver specimens of HCV RNA-negative patients in a long-term follow-up of patients after interferon-alpha treatment.