Fibrosis is the process accompanying majority of chronic diseases of liver, independent of etiological factor and leading to cirrhosis and hepatic failure. Monitoring fibrosis process by liver's biopsy is limited, so many attempts are undertaken to assess concentrations of definite proteins in blood, which could be easily accessible marker of intrahepatic process. It seems, that among others, determinations of blood concentration of aminoterminal propeptide of procollagen III--index of collagen's III synthesis and TGF-beta 1--cytokine of antiproliferative action and inhibiting hepatocytes' growth, yet inducing fibroblasts' growth and stimulating fibrosis process brings out such a possibility. The aim of the study was simultaneous determination of TGF-beta 1 and PIIINP concentration in blood of patients with chronic hepatitis B and C before interferone's therapy in comparison to healthy controls, assessment of the parameters in dependence on stage of liver fibrosis and determination of correlation between TGF-beta 1 and PIIINP. Studies were performed in 40 patients with chronic hepatitis B (CAH B) and 35 patients with chronic hepatitis C (CAH C). Significantly increased serum concentrations of TGF-beta 1 as PIIINP in both groups of patients (CAH B and CAH C; grading 2-3, staging 1-2) in comparison with control group was noted. Significant positive correlation of TGF-beta 1 and PIIINP serum concentrations in both groups of patients was observed. There was not significant changes in PIIINP serum levels in patients with hepatitis B and C in dependence on stage of liver fibrosis (staging 1 vs staging 2) but TGF-beta 1 serum levels was significantly increased in CAH B and C patients with higher stage of liver fibrosis process. On the base of obtained results, it seems that changes in TGF-beta 1 concentrations in blood reflect "grading" and "staging" and can be a marker of intensification of intrahepatic fibrosis process whereas PIIINP levels in blood have rather the relation with "grading".