The kinetics of isothermal crystallization from the melt of copolyamides 6/6.6, 6/6.T and 6/6.I was analyzed by differential scanning calorimetry at various degrees of supercooling. At the same degree of supercooling tile rate of isothermal crystallization decreases in the order of copolyamides 6/6.T, 6/6.I and 6/6.6, which suggests that the rate decreases with the increase of structural rigidity of comonomer. Avrami exponent n values were somewhat larger for copolyamides 6/6.T and 6/6.I than for copolyamide 6/6.6. It is found from the melting temperature depression that the comonomer exclusion modes is not always satisfied for the crystallization behavior of copolyamides.