In order to evaluate the evolution of transfusional hepatitis C in haemophiliacs, we performed a retrospective study of ALT levels and HCV viraemia with a RNA PCR assay in 57 patients. We found that the vast majority of HCV-infected patients remained viraemic (43/57 = 75%) and higher ALT levels correlated with HCV viraemia. Although indicators of the transfusional viral load (age, severity of haemophilia) and HBV co-infection did not correlate with HCV RNA replication, HIV seropositivity was strongly associated with persistence of HCV viraemia (23/25 = 92% in HIV-positive versus 20/32 = 62% in HIV-negative patients), without any correlation with CD4 counts. Genotyping of HCV in the 43 viraemic patients shows more frequent genotype 1 in the HIV-seropositive group (14/23) than in the seronegative group (6/20). Our data emphasize that besides the role of the immunodeficiency status, the genotypes of HCV might be involved in the differences observed in terms of HCV RNA replication between the HIV-seropositive and seronegative haemophiliacs.