Excess molar enthalpies () for mixtures of supercritical CO2 and ethanol aqueous solutions were measured at 323.15 K and 7.64 and 15.00 MPa using an isothermal high-pressure flow calorimeter. values obtained at the lower pressure are very exothermic while those obtained at the higher pressure are moderately endothermic. for CO2 + H2O mixtures at 308.15 K and 7.64 MPa and 323.15 K and 15.00 MPa were also measured. These data are examined together with data previously reported for mixtures of supercritical CO2 and ethanol aqueous solutions, vapor–liquid equilibrium data for the ternary system CO2 + H2O + ethanol and the excess enthalpy data for the three related binary systems. CO2–ethanol interactions are shown to be the main contribution to excess enthalpies when supercritical CO2 and ethanol aqueous solutions are mixed. Ternary excess enthalpies for CO2 + H2O + ethanol are also obtained. Kohler's method is used for estimating these ternary data from the excess enthalpy data of the three related binary systems.