A study was performed in 10 European health care centers in which 914 patients coinfected with hepatitis C virus (HCV) and human immunodeficiency virus (HIV) who had elevated serum alanine aminotransferase (ALT) levels underwent liver biopsy during the period of 1992 through 2002. Overall, the METAVIR liver fibrosis stage was F0 in 10% of patients, F1 in 33%, F2 in 22%, F3 in 22%, and F4 in 13%. Predictors of severe liver fibrosis (METAVIR stage, F3 or F4) in multivariate analysis were age of >35 years (odds ratio [OR], 2.95; 95% confidence interval [CI], 2.08-4.18), alcohol consumption of >50 g/day (OR, 1.61; 95% CI, 1.1-2.35), and CD4+ T cell count of <500 cells/mm3 (OR, 1.43; 95% CI, 1.03-1.98). Forty-six percent of patients aged >40 years had severe liver fibrosis, compared with 15% of subjects aged <30 years. The use of antiretroviral therapy was not associated with the severity of liver fibrosis. In summary, severe liver fibrosis is frequently found in HCV-HIV-coinfected patients with elevated serum ALT levels, and its severity increases significantly with age. The rate of complications due to end-stage liver disease will inevitably increase in this population, for whom anti-HCV therapy should be considered a priority.