The influence of human immunodeficiency virus (HIV) coinfection and hepatitis C virus (HCV) genotype distribution on HCV viral load and alanine amino transferase (ALT) levels in chronically infected patients remains unclear. In the present study, serum samples from a group of haemophiliac patients were investigated retrospectively. HCV geno- and subtyping was carried out using the Inno line probe assay (Inno LIPA, Innogenetics, Zwijnaarde, Belgium) in 87 patients positive by HCV RT PCR. Of these patients, 31 (35.6%) were HIV coinfected. HCV RNA was quantified with the HCV Monitor kit (Roche, Basel, Switzerland) in 43 patients (22 HIV-negatives, 21 HIV-positives). The most prevalent genotypes were 1 (n = 52) and 3a (n = 16) followed by genotype 2 (n = 9) and 4 (n = 3). Mixed infections were detected in 7 patients. Of genotype 1 positive samples, 24 and 23 were classified as subtype a and b, respectively. Five samples could not be subtyped. Although higher mean values of ALT were observed in genotype 1 infected patients, there was no statistically significant association between HCV genotype or subtype and liver enzymes (P > 0.05). On the other hand, statistically significant higher HCV RNA titres were observed in haemophiliacs infected with HCV genotype 1 in comparison to those infected with other genotypes (P < 0.01). No relationship was found between the presence of HIV coinfection and viral load of HCV RNA. There was no evidence that HCV infection had a more severe outcome in HIV-positive patients who had been infected with HIV and HCV more than ten years ago, even in those with very low CD4+ cell counts. No clear association between high ALT levels and large amounts of viral RNA was observed. In conclusion, a large viral load is associated with HCV genotype 1 infection; HIV coinfection has no clear effect on the intensity of HCV replication. An ongoing prospective study will evaluate the respective role of viral load, genotype, HIV coinfection and ALT level in the response to interferon therapy.