The excess molar enthalpies H-E of the liquid mixtures of (methanol + ethanol + I-propanol) and (methanol + ethanol + 2-propanol) have been measured at 298.15 K and atmospheric pressure using a flow microcalorimeter. The experimental H-E are used to test the suitability of an extended version of the UNIQUAC associated-solution model with binary parameters alone. The model requires solvation equilibrium constants for alcohols not to be the geometric mean of the self-association constants to provide better results.