In this paper, we study the kinetics of the curing of an unsaturated polyester resin initiated with MEKP by means of DSC. DSC runs were performed at different heating rates. The experimental curves were fitted using two kinetic models : one involving the concept of free-radical polymerization, and the other an empirical model that does not take into account the different steps involved in the curing. A computer program was developed to find the parameters involved in each kinetic model. The calculation algorithm uses the Runge-Kutta numerical integration and the "downhill simplex method". The experimental data are very well fitted by using both models. The activation energy values are in concordance with the values tabulated by Odian. In the model theoretical calculation, it is useful to know the decomposition rate constant of the initiator. We determined the decomposition constant by using two different methods. Both methods give similar values of the activation energy Ed and they are in agreement with those tabulated in the literature.