An homologous series of aliphatic polyureas of the type chemical structure image where the x = 2, 3, 4, 5, 6, 7, 8, 9, and 12, was prepared from hexamethylene diisocyanate and diamines. The polymers were obtained in powder form with the use of acetone as the solvent. The intrinsic viscosities of the phenolic solutions of these polyureas were found to decrease with increasing polymerization temperature. When the melting points of the polymers were plotted against the intrinsic viscosities within each species of polymer, these melting points were found to increase with the intrinsic viscosity. The curves so formed appeared to approach an asymptote.