Equilibrium molecular dynamics simulations have been used to calculate the diffusivity of simple fluid mixtures in macrovolume systems and in porous media at different temperatures, densities, and pore widths. Based on the Chapman-Enskog theory and the Heyes relationships, two correlation models, which can describe the diffusivity of simple fluid mixtures in porous media as a function of the reduced temperature, density, and pore width, are proposed. The validity of the models is evaluated by comparing the calculated diffusivity data with those from the simulation data. (C) 2004 Elsevier B.V. All rights reserved.