Abstract Copolymerizations of combinations of 1.3‐dioxolane (DOL), styrene (St) and 3.3‐bis(chloromethyl) oxacyclobutane (BCMO), and terpolymerization of these monomers were investigated with the use of Et 3 OBF 4 as an initiator. A random copolymer of DOL and St with molecular weight as high as 3 × 10 5 was prepared. By utilizing a “living” nature of the polymerization of DOL by this initiator, a block copolymer (I) consisting of a DOL homopolymer block and a DOL‐St copolymer block was synthesized by two step copolymerization in which St monomer was added to a solution of “living” DOL polymer In a similar way, a block copolymer (II) was also prepared from DOL and BCMO: Terpolymerization of DOL, St and BCMO gave a resinous material, partly insoluble in hot benzene. At least the insoluble part was confirmed to be a terpolymer by elemental analysis and solubility tests. Two step terpolymerization by adding BCMO monomer into a solution of “living” DOL‐St copolymer yielded a benzene soluble product which was supposed to be a block copolymer (III) composed of a DOL‐St copolymer block and a DOL‐St‐BCMO terpolymer block: It is concluded by the successful preparation of terpolymers of DOL, St and BCMO that the latter two monomers which do not copolymerize with each other can be incorporated into a copolymer chain through the intermediary of DOL monomer.