Nucleic acid probes bearing detectable labels are widely used in the life sciences and biotechnology to provide a sensitive means to detect, localize, measure or amplify specific nucleic acid sequences in the course of genetic or clinical analyses and molecular biology manipulations. Genetic Vectors has developed a chemical procedure for incorporation of detectable labels into nucleic acids. It is capable of attaching virtually any detectable label to nucleic acids in a configuration that does not hinder Watson-Crick bonding. This new procedure has a variety of applications, from labeling probes and primers to measuring trace levels of nucleic acids. One of the primary commercial applications of the EpiDNA(TM) technology is its use for the preparation of labeled probes and primers by direct labeling of existing polynucleotides and oligonucleotides. In the studies outlined here, we will establish basic conditions for the rapid direct labeling of nucleic acids. The results of these studies will provide the basis for development of a line of commercial products, marketed under the trademark EpiDNA(TM), including nucleic acid assays, kits for preparation of labeled probes and primers, guanine derivatives for chemical and enzymatic synthesis of labeled nucleic acids, new derivatives of detectable molecules for labeling nucleic acids and pre-labeled probes for clinical and veterinary diagnostics.