The curing reaction of the system diglycidyl ether of bisphenol A (DGEBA), an organic anhydride (HMTPA), as curing agent and a tertiary amine (DMP 30) as initiator has been studied by Thermal Scanning Rheometry (TSR) under isothermal conditions. The gel time, which is defined by several different criteria, has been found to be a good parameter to determine the activation energy of this curing process; on the other hand, the gel time depends on the concentration of the initiator. An empirical model has been used to predict the change in viscosity (eta*) of the system with time until the gelation is reached; the first-order kinetics, the apparent kinetic constant (k＇), and the activation energy before gelation have been determined. Furthermore, these results are reported together with the reaction mechanism proposed by another authors.