This study aimed to investigate whether HIV and HIV-related factors are associated with spontaneously resolved hepatitis C virus (HCV) infection and levels of hepatitis C viremia. Among 351 anti-HCV(+) injection drug users, with and without HIV infection, multivariate methods were used to evaluate whether HIV status and HIV viral load, CD4 T-cell count, and concurrent HIV antiretroviral therapy were associated with (1) spontaneously resolved HCV infection and (2) HCV RNA levels. In 186 HIV patients, decreased HCV resolution was independently associated with Black race and modestly associated with CD4 T-cell count <200 cells/ml. Among 310 patients with persistent HCV infection, higher HCV RNA levels were independently associated with HIV status but not with other HIV-related factors. HIV may be associated with persistent HCV infection in patients with low CD4 T-cell counts. Moreover, HIV is associated with increased HCV viral load, which may attenuate response to HCV antiviral treatment in coinfected patients.