Chronic hepatitis C is associated with more severe liver disease in patients coinfected with HIV, but the pathogenic mechanism of this more aggressive course is still unclear. The aim of this study was to assess the relationship of HCV genotype, viral load and epidemiological factors with the histological severity of chronic hepatitis in haemophilia patients with HCV/HIV coinfection, taking into consideration the immune status of the patients. Twenty-one HIV/HCV coinfected haemophilia patients, with mean age +/- SD 35.7 +/- 8.7 years, underwent transcutaneous liver biopsy 6-15 years (median 12 years) after HIV and 6-32 (median 21.5 years) years after HCV infection. Twelve patients were stage A (CDC), six stage B and three stage C. CD4 cells were < 50 microL(-1) in three patients (14.3%), 50-200 in 11(52.4%) and > 200 in 7(33.3%). Mean +/- SD log(10) HCV-RNA was 6.87 +/- 0.7 copies mL(-1) (range 5.4-7.9), and mean +/- SD log(10) HIV-RNA was 3.75 +/- 0.98 copies mL(-1) (range 2.7-6), at the time of liver biopsy. Minimal hepatitis was diagnosed in five patients (24%), mild in 10 (48%) and moderate in six (28%). Hepatitis stage 0-2 was found in seven cases (33%) and cirrhosis in six (29%). Statistical analysis showed a significant association of CD4 count < 50 with minimal hepatitis and of CD > 200 with mild and moderate hepatitis (P = 0.033). In addition, minimal hepatitis was found only in patients with stage C, while the majority of subjects with HIV stage A showed mild and moderate hepatitis (P = 0.003). Moreover genotype 1 was independently associated with advanced hepatitis stage (P = 0.04). No relationship was found between hepatitis severity, HIV or HCV RNA levels, patient's age and duration of HIV or HCV infection. Our results suggest that HCV/HIV coinfection may aggravate the course of hepatitis in the phase of immunocompetence, most probably through an immune mediated process. Genotype 1 seems to be associated with advanced liver disease.