In order to elucidate the clinical significance of serum hyaluronan in chronic viral hepatitis, serum hyaluronan concentrations were measured using a sandwich enzyme binding assay in 115 patients with chronic viral hepatitis. These findings were examined in relation to the results of laboratory liver tests, levels of serum markers for fibrosis and liver histological findings. Serum hyaluronan levels increased with the progress of liver disease, particularly in liver cirrhosis. There were no significant differences in serum hyaluronan levels among the cirrhotic patients according to Child's grade. Multivariate analysis showed that the significant independent predictors of serum hyaluronan were serum aspartate aminotransferase (P = 0.020), serum alanine aminotransferase (P = 0.008), serum cholinesterase (P < 0.001), particularly serum type IV collagen 7S domain (P < 0.0001), and the histological degree of liver fibrosis (P < 0.0001). These findings suggest that elevated serum hyaluronan levels are closely related to the severity of liver fibrosis. We assessed the predictive value of serum hyaluronan in differentiating cirrhosis from chronic hepatitis, constructing receiver operating curves; we found that serum hyaluronan was a better test for diagnosing cirrhosis than serum type IV collagen 7S domain and laboratory liver tests.