Poly[2-methoxy-4,6-di (2,7-naphthyloxy)-s-triazine] was synthesized by interfacial polycondensation of 2-methoxy-4,6-dichloro-s-triazine with 2,7-dihydroxy-naphthalene. The polymer was characterized by IR and UV spectra, dynamic mechanical analysis, differential scanning calorimetry, and thermogravimetric analysis. The polymer was fractionated by the fractional precipitation method and the fractions were characterized by viscometry and membrane osmometry. The polymer has a Tgof 175°C and is found to be stable up to 300°C in air. The polymer sample is found to degrade in air in two steps, and the energy of activation for the first step is around 25 kcal/mol.