The dependence of the liquid-liquid equilibria with pressure and temperature in noncritical ranges is analyzed and related with excess functions, particularly excess enthalpies and volumes. It is shown that the shape of the liquid-liquid equilibrium binary diagrams can be inferred from the concavity and sign of excess properties as functions of the composition. The application of this study to the evaluation of experimental data and models is discussed. The stationary points observed for LLE compositions in temperature and in pressure diagrams are explained in terms of excess properties. A set of criteria has been developed for determining the direction of the response for changes in pressure and temperature.