To increase the accessibility of 8-bromo-2',5'-oligoadenylates, we developed a synthesis of 2'-5'-linked oligoriboadenylates containing varying numbers of 8-bromoadenosine residues based on the use of a CPG-LCA solid support and the phosphoramidite approach. Although N6-benzoyl protection was satisfactory for incorporation of nonmodified adenine residues into 2',5'-oligonucleotides, the effective incorporation of 8-bromoadenine into such 2',5'-linked oligomers required use of a non acyl protecting group. Amidine protection of the purine exocyclic amino function proved compatible with all aspects of the phophoramidite approach and with the hydroxyl protection groups employed.