Molecular modeling methods have been applied to the structural characterization of the interaction between chiral metal complexes [Co(phen)2dppz]3+ (where phen = 1, 10-phenanthroline, dppz = dipyrido[3,2-a: 2′, 3′-c]phenazine) and the oligonucleotide (B-DNA fragment). The natures of two kinds of the binding modes, which are currently intense controversy, have been explored. Barton proposed that there is enantio-selective DNA binding by the octahedral complexes and intercalative access by these complexes from the major groove; but Norden suggested that both enantiomers bind extremely strongly to DNA from the minor groove without any noticeable enantio-selectivity. Our results support and extend structural models based upon Nordens studies, and conflict with Bartons model.