The interaction between a synthetic DNA dodecanucleotide and tris(ethylenediamine)cobalt(III) cations has been studied by Monte Carlo simulations. A simple two-state model with a single adjustable parameter is used to model the H-1-NMR chemical shift movements obtained in a parallel experimental study of the metal-ion complex-dodecamer interaction. The observed chemical shift movements, due to changes in the metal-ion complex and electrolyte concentrations, are quantitatively reproduced by this model. The simulations indicate that the binding of the Delta-enantiomer of tris(ethylenediamine)cobalt(III) cation can be mainly attributed to electrostatic forces. Furthermore, the results suggest that the enantiomeric selectivity observed in the experimental study can be explained in terms of a suitable complementarity of hydrogen-bond donors on the metal-ion complex with hydrogen-bond accepters on the dodecamer.