as little is known about liver histology in the co-infection of hepatitis c virus (hcv) and hepatitis g virus (hgv), hgv rna was investigated in 46 blood donors with hepatitis c, 22 of them with liver biopsy: co-infection hcv / hgv (n = 6) and hcv isolated infection (n = 16). besides staging and grading of inflammation at portal, peri-portal and lobular areas (brazilian consensus), the fibrosis progression index was also calculated. all patients had no symptoms or signs of liver disease and prevalence of hgv / hcv co-infection was 15.2%. most patients had mild liver disease and fibrosis progression index, calculated only in patients with known duration of infection, was 0.110 for co-infection and 0.130 for isolated hcv infection, characterizing these patients as "slow fibrosers". no statistical differences could be found between the groups, although a lesser degree of inflammation was always present in co-infection. in conclusion co-infection hcv / hgv does not induce a more aggressive liver disease, supporting the hypothesis that hgv is not pathogenic.