We used the polymerase chain reaction (PCR) to detect hepatitis D (HD) viremia in patients infected with the human immunodeficiency virus (HIV). Nineteen (9%) of 206 such patients were prospectively found to be infected by HDV. Thirty-one anti-HIV-positive patients were studied by means of PCR and the results were analysed according to HDV and hepatitis B virus (HBV) serological status. HDV-PCR was positive in five patients. Two had detectable serum HDV antigen. Four patients had anti-HD IgM and IgG antibodies. All these patients were HBs antigen-positive, and three were HBV-DNA positive. All the other patients were HDV-PCR-negative. Statistical analysis suggested more extensive liver damage and immunological impairement in HDV-PCR positive patients. In this unselected HIV-infected population, HDV-RNA detection by PCR was only evidenced in HDV infected patients in whom 5/19 were positive. This test allowed direct diagnosis of HDV viremia and will be useful for the monitoring of HDV infection.