A thermostated sapphire capillary was inserted into the exit line of a flow calorimeter. This capillary is used to visually determine the upper critical solution temperature (UCST) for acetonitrile + cyclohexane, + propane, and + butane at several pressures. The UCST results were combined with liquid + liquid results obtained earlier from breaks in the excess molar enthalpy versus mole fraction curves to obtain the liquid + liquid phase diagrams for acetonitrile + propane, and + butane at 5 and 10 MPa.