We have developed a new, rapid method for the extraction of human genomic DNA from whole blood samples. Traditionally, genomic DNA has been extracted from blood by overnight proteinase K digestion of lysed peripheral lymphocytes followed by phenol/chloroform extraction. In addition to being time consuming, the use of phenol involves inherent risks due to the toxic nature of the reagent. Our method for the extraction of DNA from whole blood uses sodium perchlorate and chloroform instead of phenol with a significant time savings realized as well as fewer hazards to the technician. Furthermore, DNA prepared by this new method is an excellent substrate for restriction endonuclease digestion and Southern hybridization analysis.