The binary vapor-liquid and liquid-liquid equilibria and molar excess enthalpies of mixtures including aniline and/or acetonitrile are correlated well with a new associated-solution model whose equilibrium constants are defined in terms of the volume fractions of chemical species. Predictions for the ternary phase equilibria and molar excess enthalpies of mixtures containing aniline and/or acetonitrile and for the ternary molar excess enthalpies of the n-butylamine + acetonitrile + 1,4-dioxane system are good with the model using binary parameters alone.