The natural history of hepatitis C virus (HCV) infection in human immunodeficiency virus (HIV)-infected patients has never been studied according to the concept of liver fibrosis progression. The aim of this work was to assess the fibrosis progression rate in HIV-HCV coinfected patients and in patients infected by HCV only. A cohort of 122 HIV-HCV coinfected patients was compared with a control group of 122 HIV-negative HCV-infected patients. Groups were matched according to age, sex, daily alcohol consumption, age at HCV infection, and duration and route of HCV infection. The fibrosis progression rate was defined as the ratio between fibrosis stage (METAVIR scoring system) and the HCV duration. The prevalence of extensive liver fibrosis (METAVIR fibrosis scores 2, 3, and 4) and moderate or severe activity were higher in HIV-infected patients (60% and 54%, respectively) than in control patients (47% and 30%, respectively; P <.05 and P <.001, respectively). The median fibrosis progression rate in coinfected patients and in control patients was 0.153 (95% confidence interval [CI], 0.117-0.181) and 0.106 (95% CI, 0.084-0.125) fibrosis units per year, respectively (P <.0001). HIV seropositivity (P <.0001), alcohol consumption (>50 g/d, P =.0002), age at HCV infection (<25 years old, P <.0001), and severe immunosuppression (CD4 count </=200 cells/microL, P <.0001) were associated with an increase in the fibrosis progression rate. In coinfected patients, alcohol consumption (>50 g/d), CD4 count (</=200 cells/microL), and age at HCV infection (<25 years old) (P <. 0001, respectively) were associated with a higher fibrosis progression rate. HIV seropositivity accelerates HCV-related liver fibrosis progression. In coinfected patients, a low CD4 count, alcohol consumption rate, and age at HCV infection are associated with a higher liver fibrosis progression rate.