Many models have been developed to describe the kinetics of the free radical polymerisation of methyl methacrylate (MMA). However, they are restricted to low temperatures, e.g., below the glass transition temperature of the polymer, T-g. In this work, kinetics of bulk and solution polymerisation of MMA were determined by differential scanning calorimetry (DSC) for temperatures above T-g, i.e. 130-165 degrees C. On the basis of our own experimental results (high temperatures) acid those published in the literature (low temperatures), it has been shown that with small modifications, the model of Achilias and Kiparissides gives a good description of kinetics for a temperature range from 20 to 165 degrees C. Furthermore, all parameters appearing in the diffusion-limited part of the kinetic rate constants have a clear physical meaning and can be evaluated in terms of physical and transport properties of the reacting species.