p-Substituted phenyl vinyl sulfides (PVS) were prepared and their radical polymerizations were investigated dilatometrically to determine some kinetic constants and to deduce the influences of the sulfur atom andp-substituents of PVS. It was found that PVS could be easily homopolymerized by ordinary radical polymerization mechanisms in the presence of 2,2′-azobisisobutyronitrile, contrary to the case of phenyl vinyl ethers, which do not homopolymerize.