Although commercially available nucleic acid amplification assays exist for three most important parenterally transmissible viruses, e.g. human immunodeficiency virus type 1 and hepatitis B and C viruses, the relatively high price of these assays obviates their use in many parts of the world. Among recent technical improvements in the field of molecular virology, real-time polymerase chain reaction (PCR) is one of the most exciting and is expected to be an alternative and a cheaper diagnostic tool for the detection of parenterally transmissible viruses. Real-time PCR allows a simultaneous amplification and quantification of specific nucleic acid sequences. This is achieved by a combination of rapid thermal cycling and cycle-by-cycle basis detection of the reaction kinetics by means of fluorimetry.