Measurements of molar enthalpy increments for (0.5H(2)O + 0.5C(2)H(5)OH) are reported. A counter-current water-cooled Row calorimeter was used to measure 76 enthalpy increments over the temperature range 373.2 K to 573.2 K at pressures from 0.1 MPa up to 11.3 MPa. Extrapolation of the gas phase measurements to zero pressure gave values in excellent agreement with the mean of the pure component ideal gas enthalpies calculated from spectroscopic data. Liquid phase enthalpy increments at temperatures in the range 423.2 K to 523.2 K and at the pressures (5.0, 10.0, and 15.0) MPa were calculated from excess enthalpy measurements combined with pure component enthalpy increments. At the pressures (5.0 and 10.0) MPa these enthalpy increments were found to be in excellent agreement with the new measurements. The boundary of the two phase region was constructed with the aid of data derived from (vapour + liquid) equilibrium measurements. Enthalpies of flash vaporization of the mixture at x = 0.5, obtained from the boundaries of two phase region, lie between the enthalpies of vaporization of the purr: components.