Interleukin-6 (IL-6) is an important cytokine in liver regeneration, and elevated levels of IL-6 have been demonstrated in patients with chronic liver diseases (CLD). Many biological effects of IL-6 depend on naturally occurring soluble IL-6 receptors. In the present study we measured the concentrations of IL-6 and its soluble receptors in the sera of patients with CLD related to hepatitis C virus (HCV) infection. We studied 77 patients with varying degrees of HCV-related CLD. Serum levels of IL-6 and its soluble receptors (sIL-6R, sgp130) were measured by enzyme-linked immunosorbent assay. Serum IL-6 and sIL-6R were elevated in patients with CLD compared with healthy subjects. Serum levels of sgp130 did not differ between patients with chronic hepatitis and healthy subjects. However, in patients with liver cirrhosis, sgp130 was significantly elevated and was positively correlated with total bilirubin and negatively correlated with cholinesterase and prothrombin time. Our study demonstrated that in patients with HCV-related CLD, serum IL-6 and its soluble receptor levels are correlated with both liver function impairment and the degree of liver fibrosis. These observations suggest that the balance of IL-6 and its soluble receptors may correspond to the state of liver damage in patients with CLD.