Reaction calorimetry is an efficient tool used to obtain kinetic, thermodn. and safety data. A reaction calorimeter, RC1e-HP350, developed in collaboration with Mettler-Toledo GmbH, allows investigating chem. reactions under supercrit. conditions. The main tech. difference, compared with a classical liq. system, is that the whole reactor vol. is occupied by the media. Heat transfer anal. in supercrit. carbon dioxide (scCO2) by the Wilson plot method shows that the behavior of the internal heat transfer coeff. in scCO2 is the opposite of the one obsd. for classical liq. In scCO2 the lower the temp. (above the crit. point) the better the internal heat transfer coeff. The evolution of scCO2 thermodynamical and transport properties near the crit. point are responsible for this behavior. The dispersion polymn. of Me methacrylate in scCO2, with the polydimethylsiloxane monomethacrylate as stabilizer, is used as a model reaction. A polymn. reaction enthalpy of -56.9 +- 2.2 kJ.mol-1 is detd., being in good agreement with previously reported data. The results presented illustrate the accuracy of the heat balance model used and emphasize the potential of reaction calorimetry for the promotion of supercrit. fluids technologies.