A united atom nonpolarizable force field for the simulation of mixtures of acetone and water is described. The force field is designed to reproduce the thermodynamics and aggregation behavior of acetone-water mixtures over the full composition range at 300 K and 1 atm using the enhanced simple point charge water model. The Kirkwood-Buff theory of solutions is used to relate molecular distributions obtained from the simulations to the appropriate experimental thermodynamic data. The model provides a very good description of the solution behavior at low (x(a) < 0.2) and high (x(a) < 0.8) acetone concentrations. Intermediate compositions display a small systematic error in the region of highest water self-aggregation, which is removed on using larger system sizes. In either case, the activity of the solution is well reproduced over the full range of compositions. (C) 2003 American Institute of Physics.