Abstract: A method for detecting the presence of an assayed nucleic acid sequence in a sample is an essentially two stage-procedure. As illustrated, in a first stage the sample is reacted in a manner which gives rise to the production of a triggering oligonucleotide where the sample contains the assayed sequence. In the second stage, the reaction product is incubated under appropriate conditions with an amplification system whereby, in the presence of triggering oligonucleotide, a large amount of a nucleic acid product is obtained. The detection of this product thus indicates the presence of the assayed sequence in the sample.