The purpose of this investigation was to study the solid-state polymerization of suitable 1,6-diene monomers, to compare the structure of the polymers with those obtained by free radical initiated solution polymerization, and to use this information in postulating the most probable conformation of the monomer in the crystal. An additional purpose was to compare the polymerization characteristics of these dienes with suitable monoolefinic counterparts. The compounds studied were dimethacrylamide, N-isobutyryl-methacrylamide, and their N-methyl and N-phenyl derivatives. Solution polymerization of all monomers and solid-state polymerization of solid monomers (N-methyl- and N-phenyl-N-isobutyrylmethacrylamide were liquids which did not polymerize) led to polymers of comparable structure in each case. Dimethacrylamide yielded a polymer consisting primarily of six-membered rings. N-Methyldimethacrylamide gave a polymer consisting predominantly of five-membered rings but up to 30= six-membered rings. N-Phenyldimethacrylamide gave a polymer containing almost exclusively five-membered rings. The formation of comparable cyclic polymers by both methods is interpreted to mean that the 1,6-diene molecules are present in the crystal in a conformation favorable for cyclopolymerization.