Based on the explicit mean spherical approximation proposed by Castro and Blum (1989) [Castro, C.S. and Blum, L., 1989. J. Phys. Chem., 93 : 7478-7482], a model with only three parameters has been developed to correlate the vapor pressure of electrolyte solutions. The cations arc considered to be hydrated with water molecules, and the effective diameter of the cations is correlated with salt concentration, while the Pauling crystal cation diameter as the asymptotic value. The anions are assumed to remain nonhydrated as suggested by Gering et al. (1989) [Gering, K.L., Lee, L.L. and Landis, L.H., 1989. Fluid Phase Equilibria, 48 : III 1391, and the Pauling crystalline anion diameter is used directly as the effective anion diameter. The proposed model has been tested with experimental data reported in the literature for 26 aqueous electrolyte solutions in the temperature range of 298 343 K and a moderate range of ionic strength. The calculated vapor pressures agree well with the experimental ones, with the overall average deviation being less than 0.42%.