A sophisticated software package for the selection of the most suitable solvents or solvent mixtures for liquidliquid extraction was developed. For the selection in particular, phase equilibrium information such as selectivity, capacity, etc. was used. For the determination of these properties, besides group contribution methods, such as UNIFAC or modified UNIFAC (Do) and the group contribution equations of state PSRK or VTPR, experimental data collected and updated in the Dortmund Data Bank (DDB) can be applied. For the final selection, pure component and mixture properties such as the surface tension, density, flash point, viscosity, etc. are accessible via DDB also. The applicability of the program package was demonstrated by means of various extraction processes of industrial importance.