Hepatitis B virus/hepatitis C virus (HBV/HCV) positive patients undergoing haemopoietic stem cell transplantation (HSCT) are at risk of hepatitis reactivation and fatal liver failure: we have conducted a retrospective study to assess the risk in 20 Italian transplant centres. A total of 90 patients infected with HBV (n=33) or HCV (n=57) receiving allogeneic (n=36) or autologous (n=54) haemotopoietic stem cell transplant (HSCT) between 1996 and 2000 were reviewed. The biochemical profiles and outcomes of infection-related liver disease were also analysed. The risk of death at 2 years was comparable when considering type of infection (3% for HBV vs 8% for HCV, P=0.6) or type of HSCT (7% for allogeneic vs 5% for autologous HHSCT, P=0.34). Hepatitis reactivation followed by resolution was more frequent in HCV+ than in HBV+ patients receiving an allograft (100% vs 16%, P=0.004). In HBV+ cases, risk of reactivation was comparable after autologous or allogeneic transplantation (66 vs 81%, P=0.3), but liver disease was more severe and occurred earlier in the autologous group. Our results indicate that HBV and HCV infection should not be taken as an absolute contraindication for HSCT and the risk of life-threatening liver complications are similar after allogeneic or autologous transplants.