Oligodeoxyribonucleotide (ODN)/polymer conjugates were obtained by covalent immobilization of various nucleic acid sequences to three different polymers. Two of them bore active ester groups for the covalent linkage via the formation of amide bonds and the third one featured aldehyde moieties for immobilization via reductive amination. The factors controlling the conjugation reaction were found to be the reactivities of the polymers and their abilities at forming hydrogen bonds with the ODNs to be tethered. It was found, as well, that the observed aggregation of the grafting reaction products was essentially due to hydrogen bonding with the nucleic bases of the tethered oligonucleotides.