AbstractIt could be shown that the structure of poly(styrylpyridine)s (PSP), which are heat resistant thermosetting resins resulting from the polycondensation of 2,4,6‐trimethylpyridine (1) with terephtalaldehyde (2), is much more complicated than that expected from this polycondensation. 2‐Styrylpyridines were synthesized from benezaldehyde (5) and 2‐methylpyridines and the stability of the respective intermediate alcohol was studied. The thermal behaviour of the styrylpyridines alone or in the presence of their precursors was studied by GPC, IR and NMR spectroscopy and by chemical analyses. It could be shown that the methyl group of 2‐methylpyridine (4) adds reversibly to the double bond of 2‐styrylpyridine (7) to form 2‐phenyl‐1,3‐bis‐(2‐pyridyl)propane (8). This side reaction takes place also in the case of the condensation of1with5. The structures and the reactivity of the condensation products of1with 1,2 or 3 molecules of5(compounds14, 17and18) were studied. The condensation product19, a component of PSP resins, was synthesized from1and2and its reactivity was studied at 200 and 250°C and compared with the non‐methylated derivative 1,4‐bis[2‐(2‐pyridyl)vinyl]benzene (25). The results of a preliminary analysis of the reactions taking place during the PS