ATRP of the first cyclic olefin, methyl 1-cyclobutenecarboxylate (MCBE), by addition polymerization in a well controlled/"living" manner is described, along with a new practical method to synthesize MCBE. The polydispersity of poly(methyl 1-cyclobutenecarboxylate) (PMCBE) synthesized by a conventional ATRP initiation system was narrow (M-w/M-n = 1.1-1.4), but M-n was usually less than half of the theoretical number-average molecular weight. However, the polymerization of MCBE initiated by a reverse ATRP initiation system, AIBN/CuBr2/dNbpy, was well controlled; the rate of polymerization was first order in monomer, and the molecular weights of the polymers were close to the designed values with very narrow polydispersities (M-w/M-n = similar to1.15). The obtained polymer PMCBE can be used as a macroinitiator to further polymerize a second monomer, such as styrene.