The synthesis, thermal stability, and the nature of the pyrolytic decomposition of polymeric azines,in which R is H and CH3, are reported. These polymers were synthesized by the continuous azeotropic method to yield yellow, insoluble, infusible brick-dust polymers, and by exchange reactions in melts to obtain dark-colored, tractable, fusible polymeric azines which, on heating, became insoluble and infusible and were converted to polystilbene-type polymers. The azine polymers were not very thermally stable; they decomposed thermally at approximately 300°C to yield substantial quantities of nitrogen with the concomitant formation of stilbene segmers in the polymer chains. The derived polymers were thermally stable and their physical characteristics paralleled those of the poly-Schiff bases. Calorimetric and kinetic data on the decomposition reaction of the polyazines are discussed.