The rate of the reactions between benzylamine and 2, 4-dichloro-(1) or 2-chloro-4-substituted-6-anilino-S-triaziazine derivatiltes (B) in tetrahydrofuran were estimated.In each case, the reaction was found to be a reactionof SN 2 process.A comparison of the rate constants was made on each of these derivatives and the deactivating effects of the substituents on the reactivity of chlorine atom were investigated, deactivating effects of substituentu were in the order -NH-nC₄H₉≈NHCH₃≈-NHC₂H5>-N(CH₃)₂>-NH₂;morpholinyl>-NHC₆H₅>-0C₂H₅≈-OCH₃. The results showed good agreements with heretofore known data but the effects of amino, mono-substituted amino and disubstituted amino groups howedno agreement with Thurstone' s data. Disc ussions were made on the relationship between the effects of substituents and the Hammett's rule.