The group contribution method modified UNIFAC (Dortmund) has become very popular because of its broad applications, and reliable predictions for vapor-liquid equilibria, solid-liquid equilibria, liquid-liquid equilibria, activity coefficients at infinite dilution, azeotropic data and excess enthalpies in a wide temperature range. Therefore, the existing parameter matrix for the modified UNIFAC method is continuously extended with the help of the Dortmund Data Bank and by carrying out systematic measurements. The new main group for sulfones, such as that required to describe systems with the selective solvent sulfolane, is introduced, as well as ten new pairs of group interaction parameters for modified UNIFAC.