The first radical polymerization of 1-methoxy-o-quinodimethane (2) generated by thermal ring-opening isomerization of 1-methoxybenzocyclobutene (1) is described. The polymerization of 1 in the presence of a radical initiator afforded an MeOH-insoluble polymer (3) in moderate yield at temperatures above 90 degrees C. The structure of the obtained polymer is consistent with a ring-opening polymerization. The yield of the polymer increased with the amount of initiator. Radical copolymerization with methyl acrylate was carried out. Treatment of 3 with acid gave poly(o-phenylenevinylene), quantitatively.