Anionic polymerizations of 5-vinyl-1,3-benzodioxole (1) and 4-vinyl-1,3-benzodioxole (2) were carried out in tetrahydrofuran at -78 degrees C with oligo(alpha-methylstyryl)dilithium and -dipotassium. The vinyl polymerizations of 1 and 2 proceeded quantitatively within 30 min. The resulting polymers had predicted molecular weights and narrow molecular weight distributions (M(w)/M(n) < 1.1), indicating the living character of the polymerization systems. These living polymers were however found not to be completely stable either for a long time (24 h) or at an elevated temperature (-30 degrees C). Well-defined block copolymers, poly(1-b-styrene-b-1), poly(styrene-b-1-b-styrene), and poly(styrene-b-2), were successfully synthesized by the sequential polymerizations. The methylenedioxy linkage of the acetal moiety of poly(1) was completely cleaved with boron tribromide-dimethyl sulfide complex in 1,2-dichloroethane to give the unstable poly(4-vinylcatechol).