The anionic polymerizations of 4-vinylphenyl tert-butyldimethylsilyl sulfide (1a), (4-vinylphenyl)methyl tert-butyldimethylsilyl sulfide (2a), and 2-(4-vinylphenyl)ethyl tert-butyldimethylsilyl sulfide (3a) were carried out in THF at -78-degrees-C. Monomers 1a and 3a undergo polymerization with initiators such as butyllithium, metal naphthalenides, and living oligomers of alpha-methylstyrene. Polymers of 1a have narrow molecular weight distributions (M(w)BAR/M(n)BAR = 1.11-1.13). Their M(n)BAR values estimated by SEC were proportional to those calculated from [M] to [I] ratios. The absolute M(n)BAR. values could not be measured, since the polymers became insoluble after repeated reprecipitation using THF-methanol, probably with partial cleavage of the S-Si bond, followed by oxidative coupling of the resulting SH groups. Polymers of 3a were stable and purified by reprecipitation. They had molecular weights predictable from [M) to [I] ratios and the narrow molecular weight distributions (M(w)BAR/M(n)BAR < 1.1). Postpolymerization also indicates that the polymerization of 3a is living. Complete deprotection of the tert-butyldimethylsilyl group from the polymer of 3a gave quantitatively a soluble linear poly[2-(4-vinylphenyl)ethyl mercaptan]. In marked contrast to la and 3a, no appreciable polymerization of 2a was observed under the same conditions.