A new and comprehensive procedure for process synthesis for binary and ter nary distillation processes with an emphasis on entrainer selection is presented. This procedure consists of two complementary methods for entrainer selection and a variety of graphical tools for the representation of various mixture properties of the given system. The methods for entrainer selection are based on (a) the concept of thermodynamic models, such as group contribution methods (e.g., modified UNIFAC), and (b) the access to a large computerized factual data bank with experimental data on activity coefficients at infinite dilution and azeotropes. Explicit criteria for the selection of solvents for azeotropic and extractive distillation are reported. With the help of residue curves and contour lines it is shown how further information far a comparison and advanced selection of entrainers can be obtained.