4-Vinylbenzocyclobutene (1) was prepared by the nickel-catalyzed coupling reaction of 4-bromobenzocyclobutene with vinylbromide in 70% yield. Radical homopolymerization of 1 at 60 degrees C for 24 h afforded poly(4-vinylbenzocyclobutene) [poly(1)] in 89% yield and radical copolymerizations of 1 with styrene (St) or methyl methacrylate (MMA) were carried out to obtain the corresponding copolymers. The Q and e values of 1 were determined from the copolymerization with MMA : Q = 1.07, e = 0.046. As a model reaction of the polymer reaction of poly(1) and poly(4-vinylbenzocyclobutene-co-styrene) [copoly(1-St)] with dienophiles, the Diels-Alder reaction of benzocyclobutene with N-phenylmaleimide (MI) or maleic anhydride (MANH) was carried out to determine the optimum reaction conditions. Under the optimum condition, the Diels-Alder reaction of poly(1) and copoly(1-St) with MI and MANH in the presence of 4-tert-butyl-catechol as an inhibitor were carried out to yield the corresponding polymers in good yields. The properties (solubilities, T-g, and temperature of 10% weight loss) of the products obtained from the polymer reaction were different from these of poly(1).