Triplex affinity capture (TAC) is an effective method for isolation of human genomic DNA in recombinant DNA technology. It is based on the formation of triple-helices between purine-rich oligonucleotides and homopyrimidine/homopurine sequences of double-stranded DNA in the presence of Mg2+3. In this procedure, double-stranded target DNA's are captured by a biotinylated oligonucleotide probe that has been bound to streptavidin-coated magnetic beads, and the capture can be released by addition of EDTA for use in PCR. Using this principle, this study extracted DNA for PCR-based DNA typing. The procedure amplified the MCT118, ACTBP2, FGA, D8S320, D11S488, and THO1 loci from the captured DNA. The researchers were able to obtain PCR-ready DNA only from such bloodstains on hard objects as could be scraped off, but not from bloodstains on a cotton cloth. Thus, the TAC approach has a restricted application in bloodstain analysis but is well-suited for paternity testing and population studies of microsatellites. 1 figure and 9 references