A novel technique based on microwave irradiation was developed to synthesize polyhydrazide and polythiohydrazide. These polymers were readily synthesized by the reaction of aromatic and aliphatic dihydrazides with urea and thiourea. The effects of microwave irradiation time, power, solvent nature, and solid content of monomers on the inherent viscosity of the polymers were investigated. The polymers were characterized by 1H-NMR and IR spectroscopy and elemental analysis. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012