Injection of illicit drugs is an important risk factor for acquiring parenterally transmitted viral infections. To investigate the prevalence of viral mono- and co-infections in intravenous drug uses (IDUs) postmortem and to evaluate the risk of potential infection to personnel involved in medicolegal practice a total number of 59 known IDUs were tested during necropsy for serological markers of hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus (HIV) as well as for the nucleic acids of the hepatitis B and C viruses, and the GB virus C (GBV-C), in blood and in the liver. Our findings showed that 90.2% cases were positive for at least one or more serological markers of the tested viruses. Seroprevalence rates of anti-HCV, HBsAg and anti-HIV were 78.4%, 32.4% and 29.7% respectively. Of the IDUs tested for serological infection markers 43.2% were positive for one, 40.5% for two and 5.4% for all three markers. Viral nucleic acids were detected in the sera of 64.4% and in the liver of 81.4% of the cases. HCV, RNA, GBV-C RNA and HBV DNA were found in 33.9%, 28.8% amd 28.8% of the serum samples and in 67.8%, 35.6% and 28.8% of the liver tissue, respectively. Active viral co-infections or triple infections were detectable in the sera of 20.3% and in the liver of 39% of the case. Results show that the sensitivity of viral nucleic acid testing postmortem strongly depends on the quality and source of material used.