The polymer literature now includes more than 500 papers dealing with cyclopolymerization and cyclopolymers, the first having appeared in 1957. A wide variety of dienes have been shown to undergo cyclopolymerization. In fact, almost all of the 1,6-dienes corresponding to the well-known vinyl monomers have now been synthesized and studied. Many of the corresponding 1,5-dienes which lead to five-membered rings on cyclopolymerization have also been synthesized and studied. In addition, both homopoly-mers of 1,4-dienes, which lead to bicyclic structures, and copolymers of 1,4-dienes with monoolefins have been synthesized and studied. Essentially all known methods of initiation of vinyl polymerization have now been used in conjunction with specific dienes in cyclopolymerization. In fact, one monomer, 2,6-diphenyl-l, 6-hexadiene, has been shown to undergo cyclopolymerization to form essentially the same polymer by anionic, radical, cationic, and coordination initiation.