The excess enthalpy of the miscible water-methanol system has been measured at 303.15 K in an isothermal batch calorimeter with vapour space. The effect of the salts NH4Cl, CdCl2 and HgCl2 on H-E was studied. A decreasing trend in excess enthalpy for NH4Cl and HgCl2 but an increasing trend for CdCl2 with increasing salt concentrations have been observed. The experimental values of H-E have been correlated using a modified Redlich-Kister equation and the binary parameters have been estimated. The deviations were calculated and reported.