We report molecular simulation results for both the excess mixing and partial molar properties of water-methanol mixtures over the entire concentration range with the particular emphasis on the low concentration ends. It is shown that the mixing properties are very sensitive to potential models and that the used realistic potentials (TIP4P for water and OPLS for methanol) give a reasonably good agreement with experiment only for volumetric properties although the qualitative trend of the partial molar volume at low concentrations is not reproduced. As regards excess enthalpy, the results are rather bad and only its sign is predicted correctly. (c) 2006 Elsevier B.V. All rights reserved.