The curing reaction of a polyester resin, using methyl ethyl ketone peroxide and cobalt octoate as promoter, has been studied by differential scanning calorimetry and thermal scanning rheometry under isothermal conditions. All kinetic parameters of the curing reaction, including the reaction order, activation energy, and the rate constant, were calculated and reported using different empirical relationships. The gel time, which is defined by several criteria, was used to determine the apparent activation energy of the process.