Polyesters with pendant primary hydroxyl groups were synthesized by polyadditions of bis(oxetane) with dicarboxylic acids. The polyaddition of bis(3-methyl-3-oxetanylmethyl) terephthalate (BOMT) with adipic acid was carried out in hexamethylphosphorictriamide (HMPA) using certain quaternary onium salts as catalysts at 140 degrees C for 12 h to produce the corresponding polyester, and tetraphenylphosphonium bromide (TPPB) showed the highest catalytic activity among quaternary onium salts used. However, the reaction did not occur without the catalyst or with triethylamine under the same conditions. The yield and the molecular weight of soluble polymer increased with increasing reaction temperature, reaction time, catalyst concentration, and monomer concentration. However, insoluble gel products were obtained when the reaction was performed under less than strict reaction conditions. Polyadditions of BOMT with sebacic acid, isophthalic acid, terephthalic acid, and 2,2＇-bis(4-carboxylphenyl)hexafluoropropane were also carried out under similar reaction conditions, and corresponding polyesters with pendant primary hydroxyl groups were obtained in good yields.