We have studied morbidity and mortality related to hepatitis C virus infection in haemophilic patients treated at our centre. 11/255 HCV seropositive patients have developed hepatic decompensation. 20 years after first exposure to lyophilized clotting factor concentrate the risk of hepatic decompensation is estimated to be 10.8% (95% CI 3.8-17.8%). There is a significantly increased risk associated with HIV infection, and also with increased age. For HIV seropositive patients the rates of decline in CD4 lymphocyte count and the development of p24 antigenaemia are significant risk factors for hepatic decompensation. Cirrhosis was seen in 9/19 HIV seropositive patients at post mortem. There was an association of cirrhosis with increased age but not with CD4 count, p24 antigenaemia, or AIDS. In conclusion, HCV infection is associated with serious liver disease in haemophilic patients, but so far this has been restricted to a minority of those at risk. HIV co-infection accelerates progression to hepatic decompensation, and we speculate that this is probably due to enhanced HCV replication in the presence of immune deficiency.