Calorimetry (adiabatic, isothermal, differential, oscillating or acoustic) is generally based on heat-flow measurements of the studied system. Most of its applications are dedicated to kinetic-parameter detn., safety studies and process optimization, phase equil. and phase transition studies. Heat flow calorimetry on the lab. scale is currently limited to low viscosity fluids. An emerging new field is concerned with the use of calorimetry in the presence of supercrit. fluids as solvent reaction, which will be named supercrit. calorimetry. Supercrit. carbon dioxide (CO2s.c.) represents an increasingly interesting media for a wide variety of reactions. To fulfill this need, a special supercrit. calorimeter has been developed in collaboration with Mettler-Toledo, Schwerzenbach, CH and some preliminary results are presented. This paper explores supercrit. calorimetry applied to the intrinsic properties of carbon dioxide in the liq., gas and esp. supercrit. phase as well as applications and theory related to reaction calorimetry. The CO2s.c. heat capacity (cp) is measured over the range of 33-112 DegC and 77-206 bar using a reaction calorimeter (RC1e, Mettler-Toledo) coupled with a high-pressure HP350 metallic reactor. Measured values are compared to theor. values obtained from Wagner and Span's equation of state. 3D representations of the predicted values for heat capacity, d. and sound speed of carbon dioxide in the fluid phase are presented.