The boron-catalyzed polymerization of dimethylsulfoxonium methylide (1) has been used to prepare telechelic polymethylene polymers. The functional polymers were synthesized by hydroboration of substituted alpha-olefins. Functional groups including biotin, carbohydrates, primary and secondary amines, and dansyl and pyrene fluorescent groups were tolerant to the reaction conditions. The living polymerization of ylide 1 was initiated and catalyzed by the organoborane. Oxidation of the resulting tris(polymethylene) organoborane produced omega-hydroxy-terminated polymethylenes. The reactions were used to produce alpha,omega-polymethylenes with molecular weights in the range of 1000-17 000 with polydispersities < 1.1.