Tri-n-butylphosphine-catalyzed polyadditions of bifunctional acetylenes having ester groups [i.e., bis(propiolate)s (5)] with diols (6) are described. Polyadditions with primary diols (6a-f) proceeded under mild conditions, and polymers having beta-alkoxyenoate moieties in-the main chain (only composed of E isomer) were obtained in almost quantitative yield. For instance, the reaction of 5A and 6a gave a polymer (7Aa) in 94% yield whose M(n) and M(w)/M(n) were estimated as 12 800 and 2.57, respectively. The obtained polymers were stable upon storage under air. Within the examined reaction conditions, more than 5 mol % of a catalyst and an appropriate concentration of monomers (>0.2 M) with stoichiometric conditions were suitable to obtain polymers with higher molecular weights. When the polyaddition was carried out with a small excess of 5, a gelation took place as a result of the cross-linking reaction of end-acetylene moieties.