Chronic hepatitis represents a frequent event after orthotopic liver transplantation (OLT). To ascertain the influence of HCV infection on the clinical and histological outcome of these patients, we have investigated the long-term outcome of 22 patients with end-stage chronic liver disease undergoing liver transplant focusing the attention on the role of different HCV genotypes in determining recurrence and severity of post-OLT liver disease. For all patients blood samples taken before OLT and 3 months, 1, 2 and 3 years after OLT were tested for antiHCV antibodies by two different enzyme-linked immuno-assays and by recombinant immuno-blot II and for the presence and type of HCV RNA by nested PCR (5' untranslated region and core gene primers). Of the 16 pre-OLT antiHCV-positive patients, 14 (87.5%) had recurrence of HCV infection while 2 cleared HCV. Pre-OLT genotype recurred in 11 of these 14 patients (2 genotype I) 8 genotype II - in 1 case associated with genotype III - and 1 genotype IV). Of the 6 pre-OLT antiHCV-negative patients, only 1 (16.6%) became persistently HCV-infected, with genotypes I and II. The recurrence of genotype II strictly related with development of severe chronic hepatitis while genotype I and IV were associated with milder forms of liver disease and were more easily cleared.