A new mode of metal-catalyzed polymerization reaction has been developed by exploiting the ability of 1,4-rhodium migration of an organorhodium(I) species. Specifically, it has been demonstrated that 3,3-diarylcyclopropenes undergo polymerization through an insertion-1,4-rhodium migration sequence by using an arylrhodium(I) initiator/catalyst to give poly(cyclopropylene-o-phenylene)s, which are difficult to synthesize by conventional polymerization methods.