This article concerns the characterization of the polymerization kinetics of an unsaturated polyester resin containing a large excess of styrene. For this type of resin, DSC measurements happen to not be satisfactory. Two complementary techniques were then used: an in situ near infrared spectroscopy and a PVT mold equipped with heat flux sensors. This article describes these two experimental devices and the methods used to obtain the experimental data. By monitoring the evolutions of unsaturated polyester and styrene conversions with near infrared spectroscopy, it was possible to identify two different chemical mechanisms occurring during the resin cure responsible for the measured two-peaks thermograms. Their relative importance was quantified. A kinetic model representative of these two coupled reactions was established and its parameters evaluated from the thermal analysis. This model was able to predict the kinetic behavior of the resin outside of the domain of study, even at high temperature, where the second peak of the thermogram vanishes while the final conversion decreases. This model was also able to simulate the resin cure during experiments with an imposed heating rate. (c) 2005 Society of Plastics Engineers.