Hepatitis C virus (HCV) is a major cause of liver-related morbidity and is strongly associated with B cell lymphoproliferative disorders. Data from epidemiological, biological and clinical investigations support the hypothesis of a pathogenetic role of HCV in at least a subgroup of patients with B-cell non-Hodgkin's lymphoma (B-NHL). Morphologically, HCV-associated B-NHL represents a variety of histological subtypes. The comprehension of the mechanisms of HCV persistence and of its role in the lymphomagenesis will be useful to set new strategies with the aim to prevent and treat HCV-associated B-NHLs. This hypothesis of a virus-induced mechanism of lymphomagenesis arises from the growing evidence that successful antiviral treatment is often linked to regression of some types of HCV-related indolent B-NHLs