To develop a method to detect HIV-1 viral RNA by amplifying a specific nucleic acid sequence. The nucleic acid sequence-based amplification (NASBA) method uses the simultaneous activity of avian myeloblastosis virus reverse transcriptase, T7 RNA polymerase and RNase H to amplify a specific nucleic acid target sequence. An in vitro cultured HIV-1 stock solution was used to validate the NASBA method and determine the variation in RNA measurement. Although NASBA is theoretically capable of specific amplification of RNA or DNA, it is most suitable for amplification of RNA, and therefore for detection of HIV-1 viral RNA.