Synthesis of two oligodeoxyribonucleotides of defined sequences, an undecamer [d(TGCACCATTCT)] and a dodecamer [d(TGGAGCCACTAT)], and tetradecathymidylic acid was described by a simple solid-phase method on a polystyrene resin. The synthesis was performed by the stepwise addition of deoxynucleoside 3'-phosphomonotriazolide to the resin, in the presence of a nucleophilic catalyst, 4-dimethylaminopyridine or N-methylimidazole. Quantitative coupling yield was consistently obtained for each cycle and the desired product was a major peak in the analysis of the final reaction by high performance liquid chromatography on Permaphase AAX.