This article describes the Curing behavior of diglycidyl ether of bisphenol-A using Cysteine (A)/ Methionine (B)/Cystine (C)/ mixture of 4,4'-diaminodiphenyl sulfone (DDS) and Cysteine/DDS and Methionine/DDS an(.] Cystine in various molar ratios as curing agent. Differential scanning calorimetry was used to Study the cure kinetics by recording the DSC scans at heating rates of 5, 10, 15, and 20 degrees C/min. The peak exotherm temperature was found to be dependent on the heating rate, structure of the amino acids and on the DDS/amino acids molar ratio. A broad exotherm was observed in the temperature range of 150-245 degrees C (EA), 155-240 degrees C (EB), and 190-250 degrees C (EC). Curing of DGEBA with mixture of amino acids and 4, 4 '-diaminodiphenyl sulfone (DDS) resulted in a decrease in characteristic curing temperatures. Activation energy Of Curing reaction is determined in accordance to Ozawa's method and was found to be dependent on the Structure of the amino acids and on the ratio of 4,4'-diaminodiphenyl sulfone (DDS) to amino acid. Thermal stability of the isothermally Cured resins was evaluated using dynamic thermogravimetry in nitrogen atmosphere. No significant change has been observed in the char yield of all the samples, but it was highest in the system cured using either Cystine alone (EC-1) or a mixture of DDS/Cystine (EC-2, EC-3, and EC-4). (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 216-225, 2009