A complete analysis of the heat flow equation in reaction calorimetry with supercritical fluids is presented. An especially developed reaction calorimeter is employed to study the challenges introduced by the supercritical state of the reaction mixture and the particularities that they generate in the calorimetric calculations. As a model reaction the free radical dispersion polymerization of methyl methacrylate is chosen. Each term of the heat flow equation is optimized with special attention to the accumulation term and the injection term. The overall heat transfer coefficient, being the most important variable of the heat flow equation, is estimated using four different approaches, both theoretical and experimental. Moreover, the injection phase of additional reactants is shown to generate undesirable temperature oscillations and an optimized injection strategy is found to eliminate the erroneous calorimetric calculations. As a result the enthalpy of reaction and the heat released by the reaction are very accurately estimated. (C) 2007 Elsevier B.V. All rights reserved.