Background. Before the introduction of combination antiretroviral therapy (cART), patients infected with the human immunodeficiency virus (HIV) rarely died of liver disease. In resource-rich countries, cART dramatically increased longevity. As patients survived longer, hepatitis C virus (HCV) infection became a leading cause of death; however, because patients with AIDS continue to have 5-fold greater mortality than non-AIDS patients, it is unclear whether HCV infection increases mortality in them.Methods.In this investigation, which is part of the Longitudinal Studies of the Ocular Complications of AIDS, plasma banked at enrollment from 2025 patients with AIDS as defined by the Centers for Disease Control and Prevention were tested for HCV RNA and antibodies.Results. Three hundred thirty-seven patients had HCV RNA (chronic infection), 91 had HCV antibodies and no HCV RNA (cleared infection), and 1597 had no HCV markers. Median CD4+ T-cell counts/L were 200 (chronic), 193 (cleared), and 175 (no markers). There were 558 deaths. At a median follow-up of 6.1 years, patients with chronic HCV had a 50 increased risk of mortality compared with patients with no HCV markers (relative risk [RR], 1.5; 95 confidence interval [CI], 1.2-1.9; P =. 001) in an adjusted model that included known risk factors. Mortality was not increased in patients with cleared infection (RR, 0.9; 95 CI,. 6-1.5; P =. 82). In patients with chronic HCV, 20.4 of deaths were liver related compared with 3.8 in patients without HCV.Conclusions.Chronic HCV infection is independently associated with a 50 increase in mortality among patients with a diagnosis of AIDS, despite competing risks. Effective HCV treatment may benefit HIV/HCV-coinfected patients with AIDS.