Histogram-reweighting Monte Carlo simulations in the grand canonical ensemble are used to determine pressure-composition diagrams for diethylamine + methanol, diethylamine + acetone and diethylamine + acetonitrile. Simulations were unable to predict the polyazeotropy found in the diethylamine + methanol mixture at 398 K or the minimum pressure azeotropy found at 348 and 298 K. Simulation predictions of the pressure-composition behavior of diethylamine + acetone and diethylamine + acetonitrile, however, were found to be in close agreement with experiment. Simulations in the isobaric-isothermal ensemble were used to determine the structure of the liquid phase for each of the mixtures described previously and revealed significant association taking place between unlike species.