A summary is reported on alloy thermodynamics with special reference to the measurements and evaluation of the formation enthalpies by means of calorimetric techniques. Also, advantages and drawbacks of direct and indirect reaction calorimetry are presented and discussed on the basis of the work in progress in the authors' laboratory. Comments are finally made about the problems of the calibration, intercalibration and assessment of the thermochemical data. Importance is given to the peculiar difficulties of alloy thermochemistry and to the need for a strict determination of the composition (elemental and phase composition) of the sample and of its equilibrium state.