Summary. Hepatitis C virus (HCV), which is both a hepatotropic and a lymphotropic virus, has been proposed as a possible causative agent of mixed cryoglobulinaemia. This ‘benign’ lymphoproliferative disorder can switch over to a malignant B-cell non-Hodgkin's lymphoma (NHL). Therefore HCV infection has been investigated in a series of 50 unselected Italian patients with B-cell NHL. Antibodies against HCV were found in 30% of NHL and HCV viraemia in 32% of cases. HCV-related markers were detected in 34% (17/50) of our NHL patients; this prevalence is particularly significant when compared with HCV seropositivity in Hodgkin's lymphoma (3%) and healthy controls (1.3%).