In boranophosphate-oligodeoxynucleosides (BH(3)(-)-ODN) a borane group replaces one of the two non-bridging oxygen atoms in the phosphodiester backbone of the naturally occurring congener. The chemical and biophysical properties of BH(3)(-) ODN are reviewed, as are their interactions with enzymes such as DNA polymerases, exo- and endonucleases, and ribonuclease H. Three approaches to synthesis of BH3- ODN are described: in solution, on solid supports, and by template directed enzymatic polymerization of appropriately modified nucleoside triphosphates. Comparisons are made to other members of the family of phosphorus modified nucleic acids, the phosphorothioates and methyl phos phonates. The potential applications of boranophosphate modified compounds to antisense therapeutics and DNA sequencing are discussed.