Vitrification of a reacting thermosetting system occurs when its glass transition temperature, T-g, rises to the reaction temperature, T. This phenomenon can occur in both isothermal and non-isothermal conditions, depending on the temperatures or heating rates used, the reactivity of the system, and the evolution of T-g with conversion. After vitrification, the reaction proceeds in mobility-restricted conditions. In non-isothermal experiments devitrification is observed when the reaction temperature again surpasses T-g of the vitrified resin.The cure process of two epoxy thermosetting systems and an inorganic polymer glass has been studied using modulated temperature differential scanning calorimetry (MTDSC). A normalized mobility factor, which is directly based on the experimental heat capacity evolution, is proposed. For both organic resins, it is shown that the points for which this mobility factor equals 0.5 can be used to quantify vitrification and devitrification. Preliminary results indicate a relation between the evolution of the heat flow phase and the chemorheological transformations.The mobility factor derived from the heat capacity is compared to a normalized diffusion factor calculated using the nonreversing heat flow and chemical kinetics modelling. For the organic resins studied, both factors coincide. Therefore, the mobility factor can be used as a direct measurement of the change in the rate of reaction due to mobility restrictions when T-g of the reacting system approaches T.Isothermal and non-isothermal MTDSC experiments enable the reaction mechanism, the vitrification and devitrification process, and models for diffusion control to be studied, and temperature-time transformation or continuous-heating transformation diagrams for improved thermoset processing conditions to be developed.