Measurements of the heat capacity and relative enthalpy were made on aluminum carbide (Al4C3) from 15 to 1173 °K. The thermodynamic properties were calculated up to 2000 °K from the data by judicious extrapolation above 1173 °K. In conjunction with the heat-of-formation data on Al4C3 obtained by King and Armstrong and by Mah, second- and third-law analyses have been made of the thermodynamics of several high-temperature vapor-equilibrium reactions involving Al4C3.