We developed a rapid method designated TargetDetection Assay (TDA) to determine DNA binding sites for putative DNA binding proteins. A purified, functionally active DNA binding protein and a pool of random double-stranded oligonucleotides harbouring PCR primr sites at each end are included the TDA cycle which consists of four separate steps: a DNA protein incubation step, a protein DNA complex separation step , a DNA elutfon step and a polymerase chain reaction (PCR) DNA amplification step. The stringency of selection can be increased in consecutive TDA cycles. Since tiny amounts of retained DNA can be rescued by PCR, buffer systems, salt concentrations and competitor DNA contents can be varied In order to determine high affinity binding sites for the protein of choice. To test the efficiency of the TDA procedure potential DNA binding sites were selected by the DNA binding protein SP1 from a pool of oligonucleotides with random nucleotides at 12 positions. Target sites selected by recomblnant SP1 closely matched the SP1 consensus site. If DNA recognition sites have to be determined for known, mutated or putative DNA binding proteins, the Target Detection Assay (TDA) is a versatile and rapid technique for consideration.