The reaction of diepoxides, diglycidylaniline (DGA), or diglycidyl ether of Bisphenol A (DGEBA) with aniline was followed using HPLC and SEC. The effect of molar ratio of reagents, dilution of the system, reaction temperature, and the difference between the reaction mechanisms for DGA and DGEBA systems on the reaction kinetics and molecular weight evolution is discussed. Molecular weights of the DGA-aniline polymers were by an order of magnitude lower than those of the DGEBA-aniline polymers due to the formation of small cyclic products in the former case. Also, a reduction in M(n) with increasing tem perature, dilution, and diluent polarity is brought about by a greater tendency toward cyclization under these conditions. Theoretically calculated molecular weight evolution during the reaction is in satisfactory agreement with the experiment.