A force field for the simulation of mixtures of sodium chloride and water is described. The model is specifically designed to reproduce the experimentally determined Kirkwood-Buff integrals as a function of salt concentration, ensuring that a good representation of the solution activity is obtained. In addition, the model reproduces many of the known properties of sodium chloride solutions including the density, isothermal compressibility, ion diffusion constants, relative permittivity, and the heat of mixing. The results are also compared to other common sodium chloride force fields. (C) 2003 American Institute of Physics.