Coinfection with hepatitis C virus (HCV) and human immunodeficiency virus (HIV) is associated with an accelerated course of HCV infection and a faster progression to severe liver disease. We have investigated whether the development of liver disease in coinfected patients is associated with specific chemokine and cytokine production. Four cohorts— HCV/HIV-coinfected patients, HCV-monoinfected patients, HIV-monoinfected patients, and healthy control subjects— were studied. Serum levels of the 10-kDa interferon-g-inducible protein (IP-10) were higher in all 3 groups of infected patients than in control subjects (P < .0001). HCV/HIV-coinfected patients had significantly higher IP-10 levels than monoinfected patients. In HCV-monoinfected patients, liver fibrosis scores and liver enzyme levels were positively correlated with IP-10 levels. Elevated IP-10 levels are associated with and may contribute to liver damage in bothHCV-monoinfected and HCV/HIV-coinfected patients.