Due to shared risk factors for transmission, coinfection with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) is a very common event. The prevalence of HCV infection among HIV-positive patients averages about 35% in the United States and Europe, but in clinical populations where there is a great prevalence of intravenous drug use as a risk factor for acquiring HIV, this value may be as high as 80-90%. Several studies have confirmed that HIV coinfection accelerates the natural course of chronic hepatitis C and an increased risk of liver cirrhosis, hepatocellular carcinoma, and decompensated liver disease has been found in coinfected subjects. Other studies have shown an increased risk of progression to acquired immunodeficiency syndrome (AIDS) and AIDS-related death among HIV-HCV-positive persons, suggesting that HCV coinfection may accelerate the course of HIV disease. In addition, hepatitis C may affect the management of HIV infection, increasing the incidence of liver toxicity associated with the antiretroviral regimens. The optimal therapeutic approach to HCV infection in HIV coinfected patients is still uncertain, because of the complex pathogenesis of both infections, potential drugdrug interactions, and the poor literature and information available about safety and efficacy of an interferon (IFN) and ribavirin combination in this clinical population. Available data show that the sustained virological response rates in coinfected persons treated with standard IFN plus ribavirin range from 18-40%, and several studies with pegylated IFN plus ribavirin are ongoing.