Hepatitis-associated aplastic anaemia (HAAA) is usually related to non-A, non-B hepatitis agents but the prevalence of anti-hepatitis C virus (HCV) antibodies is similar in HAAA and aplasia of other origins according to the results of the ELISA 1 assay. This fact could reflect either that HCV is not involved in HAAA or that HAAA-associated defective immune function could yield false negative assays despite on-going HCV infection. To test these hypotheses, we compared 19 patients with HAAA, including three ELISA 1-positive, to 23 patients with aplasia of known and unknown origin, including eight ELISA 1-positive, who were matched for age, sex and blood transfusion units. HCV infection was searched for by the second-generation recombinant-immunoblot assay (RIBA2), and by the polymerase chain reaction which detects HCV viraemia. HCV viraemia was detected in four among the 19 patients with HAAA and in six among the 23 patients with aplasia of other causes. HCV does not clearly appear responsible for hepatitis-associated aplastic anaemia which could be due to non-A, non-B, non-C hepatitis virus. HCV viraemia is frequent in severe aplastic anaemia, even without detectable anti-HCV antibodies, and reflects mainly transfusion-associated HCV infection.