Synthetic routes and properties of polyparabanic acid were studied. As model compounds, N,N'-dimethylparabanic acid and N,N'-diphenylparabanic acid were prepared by the reaction of N,N'-dlmethyl urea and N,N'-diphenyl urea, respectively, with oxalyl dichloride in the presence of pyridine as a catalyst. The N-substituted parabanic acids were characterized by IR, ¹H-NMR, Mass spectroscopy and elemental analysis. Various polyureas were synthesized via polyaddition reaction of 1,6-hexamethylene diisocyanate with aliphatic or aromatic diamines In DMF solution. Then, the polyureas were treated wlth oxalyl dichloride to yield polyparabanic acids. Formation of polyparabanic acid was confirmed by the appearance of IR absorption at 1730 cm^-1 and 1780 cm^-1 which were assignable to the carbonyl stretching peaks of 5-membered ring in polyearabanic acld. Inherent viscosities of the obtained polyparabanic acids were in the range of 0.15∼0.48 dL/g and the TGA data revealed 10% weight losses at 370∼458℃ whereas those of polyureas were in the range of 0.29∼0.71 dL/g and 235∼301℃ respectively.