The curing of diglycidyl ether of bisphenol A (DGEBA) with N,N'-bis-(4-aminophenyl)-1,4-benzoquinone diimine (Q) was investigated as a function of diamine concentration. The glass transition temperature (T g ) of the cured resin was determined by DSC. The maximum value of T g (170°C) was obtained when a stoichiometric amount of Q was used. At low phr of diamine T g was very low. This may be due to incomplete curing of DGEBA. The activation energy of curing as determined by multiple heating rates was found to be 102 kJ mol -1 . The curing of DGEBA with mixed diamines, i.e. Q and 4,4'-diaminodiphenylsulfone (DDS) (stoichiometric amount), was also investigated. A decrease in the onset temperature of curing and a broadening of the exotherm were observed when mixed diamines were used. The cured resins were stable up to 330°C and decomposed in a single step. The char yield at 800°C of DGEBA cured with Q was high (29%).