As it is very well known, especially when dealing with the simulation and design of distillation processes and columns, it is essential to know the limitations defined by the vapor-liquid equilibrium (VLE) of the system under consideration. This paper uses a new straightforward algorithm to calculate and completely define the distillation boundaries in different ternary azeotropic systems. The method allows, using cubic splines, the calculation of different distillation trajectories and the selection of those corresponding to the searched distillation boundaries. The algorithm has been applied to eight ternary liquid-vapor systems to test its validity. To simplify the optimization process, an empirical but very accurate equation has been used to calculate the VLE.