In order to analyse the prevalence and significance of cryoglobulinaemia in patients with chronic hepatitis C virus (HCV) infection and the possible relationship of cryoglobulinaemia with the genotypes of HCV, we studied 89 patients with chronic HCV infection, 42 healthy controls and 22 patients with alcoholic cirrhosis. The patients with HCV were divided into three different groups according to the presence of cirrhosis and alanine aminotransferase levels. Moreover, in 20 patients with HCV and cryoglobulinaemia, HCV RNA sequences were quantified in serum and in cryoprecipitate. Cryoglobulins were detected more frequently in patients with chronic HCV infection than in healthy controls (42.6% vs. 4.7%; P<0.0001). Cryoglobulins were present in 68.4% of patients with HCV-related cirrhosis, which was nearly twice the figure in noncirrhotic HCV-infected patients and alcoholic cirrhotic patients. There were no differences in age, sex, aminotransferase levels or HCV genotype distribution in HCV-infected patients with or without cryoglobulinaemia. Only 13% of patients with chronic HCV infection and cryoglobulins showed symptoms of cryoglobulinaemia. There was a linear association between HCV RNA concentration in sera and in cryoprecipitates (P<0.0005). Patients with chronic HCV infection had a high prevalence of cryoglobulinaemia, especially in advanced forms of the disease, but clinical findings are few. There was no relationship with the genotype of HCV. The presence of HCV RNA in cryoprecipitates supported the hypothesis on the aetiological role of HCV in mixed cryoglobulinaemia.