To establish the optimum conditions for obtaining high molecular weight polyacetals by the self-polyaddition of vinyl ethers with a hydroxyl group, we performed the polymerization of 4-hydroxybutyl vinyl ether (CH2=CH-O-CH2CH2CH2CH2-OH) with various acidic catalysts [p-toluene sulfonic acid monohydrate, p-toluene sulfonic anhydride (TSAA), pyridinium p-toluene sulfonate, HCl, and BF3OEt2] in different solvents (tetrahydrofuran and toluene) at 0 degreesC. All the polymerizations proceeded exclusively via the polyaddition mechanism to give polyacetals of the structure [-CH(CH3)-O-CH2CH2CH2CH2-O-](n) quantitatively. The reaction with TSAA in tetrahydrofuran led to the highest molecular weight polymers (number-average molecular weight = 110,000, weight-average molecular weight/ number-average molecular weight = 1.59). 2-Hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, cyclohexane dimethanol monovinyl ether, and tricyclodecane dimethanol monovinyl ether were also employed as monomers, and polyacetals with various main-chain structures were obtained. This structural variety of the main chain changed the glass-transition temperature of the polyacetals from approximately -70 degreesC to room temperature. These polyacetals were thermally stable but exhibited smooth degradation with a treatment of aqueous acid to give the corresponding diol compounds in quantitative yields.