In 1987 a total of 89 intravenous drug addicts were admitted to medico-legal autopsy at the University Institute of Forensic Medicine in Copenhagen. Totally 10 cases were reactive by the Elisa test and five of these, or 7% of the total material tested, could be confirmed by the immuno-blotting test. The other five cases must be considered as false positive, possibly due to antibodies against cellular antigens. Among the five real positive cases, four were known before-hand while in one case the HIV-positivity was not known. These findings - together with the possibility of false negative reactions - especially regarding persons with acute HIV-infection, requires special precautionary measures when autopsies of drug addicts are performed.