BACKGROUND In HIV/HCV co-infected patients, HIV-1 gp120 activates human hepatic stellate cells (HSCs) which play a key role in fibrosis pathogenesis. It is still unclear whether pro-fibrogenic effects are more attributable to X4 or R5 strains in vivo. OBJECTIVE To assess if HIV-1 X4 or R5 variants are associated with a different progression of fibrosis. METHODS A total of 105 HIV/HCV co-infected patients were submitted to gp120 sequencing on proviral DNA and classified as X4 or R5 based on g2p (20% false positive rate). The fibrosis evolution was retrospectively determined by means of APRI and FIB-4 scores at 3-month intervals from the first anti-HCV-positive test. The association of co-receptor tropism with increased fibrosis scores was evaluated by linear mixed models. RESULTS X4 variants were found in 41 patients (39%). The median observation period was similar in X4 and R5 patients (17 years). No difference was observed between the two groups of patients, except for nadir CD4 which was lower in X4 compared to R5 (percentage, p=0.005, and absolute number, p=0.005). X4 and R5 patients did not significantly differ for FIB-4 and APRI score over time (p=0.5, and p=0.1, respectively). No association between HCV-RNA levels over time and co-receptor tropism was noted (p=0.9). Conversely, a significant correlation of fibrosis scores with gamma-glutamyl transferase levels, lower current CD4 count, HIV viremia and use of antiretrovirals was observed. CONCLUSIONS This retrospective analysis of fibrosis evolution did not support the evidence of a differing pro-fibrogenic activity for X4 and R5 HIV-1 variants in HIV/HCV co-infected patients.