ABSTRACT: The incidence and determinants of hepatic decompensation have been incompletely examined among patients co-infected with HIV and hepatitis C virus (HCV) in the antiretroviral therapy (ART) era, and few studies have compared outcome rates with those of patients with chronic HCV alone.To compare the incidence of hepatic decompensation between antiretroviral-treated patients co-infected with HIV and HCV and HCV-monoinfected patients and to evaluate factors associated with decompensation among co-infected patients receiving ART.Retrospective cohort study.Veterans Health Administration.4280 co-infected patients who initiated ART and 6079 HCV-monoinfected patients receiving care between 1997 and 2010. All patients had detectable HCV RNA and were HCV treatment-naive.Incident hepatic decompensation, determined by diagnoses of ascites, spontaneous bacterial peritonitis, or esophageal variceal hemorrhage.The incidence of hepatic decompensation was greater among co-infected than monoinfected patients (7.4% vs. 4.8% at 10 years; P < 0.001). Compared with HCV-monoinfected patients, co-infected patients had a higher rate of hepatic decompensation (hazard ratio [HR] accounting for competing risks, 1.56 [95% CI, 1.31 to 1.86]). Co-infected patients who maintained HIV RNA levels less than 1000 copies/mL still had higher rates of decompensation than HCV-monoinfected patients (HR, 1.44 [CI, 1.05 to 1.99]). Baseline advanced hepatic fibrosis (FIB-4 score >3.25) (HR, 5.45 [CI, 3.79 to 7.84]), baseline hemoglobin level less than 100 g/L (HR, 2.24 [CI, 1.20 to 4.20]), diabetes mellitus (HR, 1.88 [CI, 1.38 to 2.56]), and nonblack race (HR, 2.12 [CI, 1.65 to 2.72]) were each associated with higher rates of decompensation among co-infected patients.Observational study of predominantly male patients.Despite receiving ART, patients co-infected with HIV and HCV had higher rates of hepatic decompensation than HCV-monoinfected patients. Rates of decompensation were higher for co-infected patients with advanced liver fibrosis, severe anemia, diabetes, and nonblack race.National Institutes of Health.