Anionic polymerization of 4-[(4-(4-vinylphenyl)butoxy)methyl]-1-methyl-2,6,7-trioxabicyclo-[2.2.2]octane (3) was carried out in THF at -78 degrees C for 10 min with oligo(alpha-methylstyryl)lithium, -dilithium, -potassium, and -dipotassium. Poly(3) was quantitatively obtained in each case, and the resulting polymers possessed predicted molecular weights and narrow molecular weight distributions (M(w)/M(n) < 1.1), indicating the living character of the polymerization of 3. By the sequential anionic copolymerization of 3 and styrene, well-defined block copolymers were successfully synthesized. The deprotection of poly(3) was performed by treating with 2 N HCl in THF for 30 min and subsequently with 10% NaOH(aq) in MeOH for 30 min. The bicyclic ortho ester moiety of poly(3) was completely cleaved to give a poly[2-(((4-(4-vinylphenyl)butyl)oxy)methyl)-2-(hydroxymethyl)- 1,3-propanediol] bearing three hydroxyl groups in each monomer unit.