Abstract: A straightforward method to characterize a nucleotide sequence of a defined DNA region is described. A purified segment representing the defined region is subjected to repeated cycles of amplification (PCR) using a single primer complementary to a portion of the segment under conditions of low stringency and high polymerase and primer concentrations. PCR under these conditions results in a mixture of amplified DNA molecules the composition of which is characteristic of the DNA segment assessed. Determination of the composition of the mixture can be obtained by subjecting the mixture to standard chromatographic or electrophoretic techniques to obtain a pattern of fragments which represents a "signature" of the nucleotide sequence.