The histological study on the reciprocal influence of chronic hepatitis C (HCV) and/or delta (HDV) on liver damage in a cohort of 134 HIV-HBV co-infected patients concluded on a significant association between HDV co-infection (noted in 13 patients) and Metavir F3-F4 liver fibrosis score [odds ratio (OR) = 7.08, 95% confidence interval (CI) = 1.06-47.28 for HBV-HDV, OR = 10.02, 95% CI = 1.03-97.42 for HBV-HCV-HDV, compared to OR = 1.76, 95% CI = 0.50-6.17 for HBV alone]. Co-treatment of other multiple viral hepatitis infections should also be taken into consideration, especially in the case of chronic HDV.