The heat flow reaction calorimetry technique was developed for reactions with supercrit. fluids and was applied to monitor the free-radical dispersion polymn. of Me methacrylate in supercrit. carbon dioxide (scCO2). The main math. equation for the calorimetric calcns. was modified to take into account the particularities linked to the supercrit. nature of the solvent. As a result, important heat transfer variables, such as the overall heat transfer coeff., can be measured at the actual reaction conditions. This information is later used to calc. the heat released by the reaction and thus monitor its evolution. The robustness and accuracy of the technique allowed also investigating the effects of several reaction parameters. Finally, the obtained data were used to illustrate the importance of pressure as far as the safety of the reaction is concerned.