Recent reports have suggested an increased risk of acute hepatitis C (AHC) infection in homosexual HIV-infected men and that early treatment with interferon-alfa, alone or associated with ribavirin, significantly reduces the risk of chronic evolution. A retrospective analysis of 38 HIV-infected patients who were consecutively diagnosed as developing AHC, defined by both seroconversion of anti-hepatitis C virus (HCV) antibodies and detection of serum HCV-RNA in those with previous negative results. Thirty-six patients were men with history of unprotected sexual intercourse with men and two were women with sexual and nosocomial risk factors. AHC infection was asymptomatic in 26 patients; asthenia and jaundice were the most frequent symptoms. HCV genotype 1 was present in 19 patients and genotype 4 in 14 patients. Thirty-five patients received early antiviral treatment with pegylated interferon-alfa associated with ribavirin; 15 of the 32 patients who completed the follow-up (47%) achieved a sustained virological response, as defined by undetectable HCV-RNA 6 months after the end of therapy. There is a risk of sexual transmission of HCV in HIV-infected men who have sex with men. In our experience, early treatment of AHC with pegylated interferon-alfa plus ribavirin in HIV patients achieves poor results.