Injection drug use has been the most growing rout of drug abuse in Iran in the past decade and it has been responsible for the transmission of HIV virus in more than two third of cases. The aim of the present study was to determine the prevalence of HIV and hepatitis B in a group of IDU cadavers and to compare the results to a group of cadavers of the normal population. In a case-control study the blood samples of the cadavers of 400 randomly chosen IDUS and 400 other cadavers as control group were checked for HBS antigen and Anti HIV antibody in the forensic medicine center of Tehran. The prevalence of HIV and HBV infection was compared in two groups according to their demographic characteristics. The number of HIV and HBV positive cadavers was significantly higher in the IDU group than the controls (6.25% vs 0.5%, P