Excess enthalpy measurements on four ionic liquid (1-ethyl-3-methylimidazolium thiocyanate, 1-ethy1-3-methylimidazolium diethylphosphate, ethyl(tributyl)phosphonium diethylphosphate, and 1-hexy1-3-methylimidazolium trifluoromethanesulfonate) + water mixtures are reported. Heat capacities and densities of seven pure ionic liquids were measured. These measurements of imidazolium- and phosphonium-based ionic liquids are compared to our previous physical property measurements.