The monomers, N,N''-bis(aminoethyl) dodecanedioamide and N,N,N'',N''-bis(diethyleneimino) dodecanedioamide, were synthesized. The amino-terminated polyamide and copolyamide of low molecular weight were obtained via amide-interchange reactions of the two monomers. The kinetics of polyamidation and copolyamidation by amide interchange reactions were found to be the second-order with respect to the concentration of amino(or imino) and amide groups in the monomers at the initial stage of the reactions. The composition diagram was constructed by the reactivity ratios, which were calculated from the four rate constants determined by the derived equation for the copolycondensation.