Anemia is a significant adverse effect of current hepatitis C treatment and may be a particular problem for HIV-infected patients, in whom there is a high prevalence of disease- or drug-related anemia at baseline. Hepatitis C treatment-induced anemia in HIV-HCV-coinfected patients can lead to ribavirin dose reduction or premature discontinuation of hepatitis C therapy, limiting sustained virologic response rates. Mean decreases in hemoglobin levels during hepatitis C treatment appear to be less in HIV-HCV-coinfected patients than in HCV-monoinfected patients, but any decrease in hemoglobin level may be more of a problem for coinfected patients. Thus, close monitoring of the hemoglobin level and appropriate management of the anemia that may develop in HIV-infected patients during hepatitis C therapy is essential.