Serum levels of haptoglobin, an acute phase protein, in usually increased in patients with inflammation and decreased in patients with intravascular hemolysis. Changes in haptoglobin serum levels were also observed in patients with liver disease. The aim of this study was to evaluate the serum level of haptoglobin in patients with chronic viral hepatitis C. Haptoglobin serum levels were measured by rate nephelometry in 34 patients with histologically proven chronic viral hepatitis C and in 30 controls. Haptoglobin serum levels were lower in patients than in controls (0.56 +/- 0.36 versus 0.90 +/- 0.35 g/L, P < 0.001). In patients with chronic hepatitis but without cirrhosis, haptoglobin serum levels were decreased as well. Haptoglobin serum levels were positively correlated to prothrombin index (P < 0.001) and negatively correlated to the histology activity index of Knodell (P < 0.001), and especially to scores of fibrosis (P < 0.001) and periportal necrosis (P < 0.05). Red cell count, indirect bilirubin level, and reticulocyte count, as markers of hemolysis, were similar in patients and controls. We conclude that determination of haptoglobin serum levels may be useful in the evaluation and the follow-up of patients with chronic viral hepatitis C.