BACKGROUND: The possible markers of liver fibrosis (plasma YKL-40, PIIINP, MMP-2 and TIMP-1) were measured at the start (t0) and end of treatment (t12) with alpha-interferon and ribavirin and repeated at 6-months follow-up (t18) in 51 patients with chronic hepatitis C. METHODS: We evaluated 1) whether treatment response is reflected by a decrease in these markers during antiviral therapy; 2) whether these markers reflect the activity of the disease; and 3) whether these markers could be used as predictors of the treatment response. RESULTS: Baseline plasma YKL-40, MMP-2, PIIINP and TIMP-1 were significantly increased in patients compared to normal controls. In responders (n = 30), plasma YKL-40 (P < 0.05), MMP-2 (P < 0.05) and TIMP-1 (P < 0.001) decreased significantly at t18, and no changes were observed at t12. Plasma PIIINP was unchanged in responders. In non-responders (n = 19), plasma MMP-2 (P < 0.01) and TIMP-1 (P < 0.01) decreased significantly at t18, whereas plasma YKL-40 and PIIINP were unchanged. The markers were significantly correlated at baseline (P < 0.001). Plasma PIIINP at baseline could predict treatment response (P = 0.01). CONCLUSIONS: Response to antiviral treatment is associated with a decrease in the fibrogenetic markers, but the markers do not reflect the biochemical disease activity during treatment. Baseline plasma PIIINP was the only marker predicting treatment response.