Poly(cyanurate)s (P-1-P-4) containing triazine groups in the main chain and pendant chloromethyl groups in the side chain were synthesized by the polyaddition of bis(epoxide)s with 2,4-dichloro-6-(diphenylamino)-s-triazine (DPAT) using quaternary onium salts as catalysts. The polyaddition of diglycidyl ether of bisphenol-A (DGEBA) with DPAT proceeded smoothly in chlorobenzene at 100 degrees C for 12 h to give P-1 with M-n = 19,000 in a 92% yield, when tetrabutylammonium chloride (TBAC) was used as a catalyst. However, no reaction occurred without a catalyst or with triethylamine alone under the same reaction conditions. Polyadditions of other bis(epoxide)s with DPTA also proceeded smoothly using 5 mol % of TBAC as a catalyst in chlorobenzene to produce corresponding polymers (P-2 approximate to P-4) in high yields under similar reaction conditions.