The thermal behavior of mixtures of bis(4-maleimidophenyl) (A) with bis(4-isomaleimidophenyl)methane (C) and their mixture with 4,4'-diaminodiphenyl methane (D) were investigated by differential scanning calorimetry. The study of the binary system A/C in different proportions led us to determine an eutectic mixture at a molar fraction of C in the range of 0.7-0.9. The ternary ACD mixtures showed themselves able to participate in three principal reactions: polyaddition, ring-opening addition, and homopolymerization. In each mixture studied the addition of diamine changed the melting point and maximum polymerization temperatures in the sense of a general decrease. The properties of the networks were studied by thermal analysis and through evaluation of water absorption. (C) 2003 Wiley Periodicals, Inc.