In order to improve the thermal resistance of diglycidyl ether of bisphenol-A (DGEBA), phosphorus-containing di- and tri-amines, i.e., bis (3-aminophenyl) methyl phosphine oxide (B) and tris (3-aminophenyl) phosphine oxide (T), were used as curing agents. The effect of phosphorus content on the curing characteristics and char residue of cured resins in nitrogen atmosphere was evaluated by using different molar ratios of conventional curing agent, i.e. 4, 4 ' -diaminodiphenyl sulfone (D) and amine B or T. Activation energy of curing, as evaluated by using the multiple heating rate method, was lowest when triamine T (61.0 kJmol(-1)) was used as hardener and was highest when D (68.7 kJmol(-1)) was used.