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The formation of polymers with erythro-meso structures, which could not be obtained from propenyl ethers with BF3O(C2H5)2, was studied by 13C-NMR spectroscopy on poly(ß-substituted vinyl ether)s obtained under a variety of conditions of polymerization. It was established that poly(cis-ethyl propenyl ether) obtained with Al2(SO4)3–H2SO4 complex in toluene at 0°C was a highly stereoregular polymer with an erythro-meso structure. Cis-2-chlorovinyl ethyl ether and cis-methyl and ethyl butenyl ethers also yielded polymers with erythro-meso structures under the same conditions. In addition, with BF3O(C2H5)2 at ?78°C these three cis isomers produced amorphous polymers with threo-meso, racemic, and, in a few cases, erythro-meso structures, whereas cis-ethyl propenyl ether produced polymers with only threo-meso and racemic structures by the same catalyst. On the other hand, all trans isomers produced stereoregular polymers with threo-meso structures with BF3O(C2H5)2 at ?78°C, regardless of their ß-substituents; no erythro-meso structures were found in the polymers obtained.