The paper presents the results of a cooperation between the University of Dortmund and GHN, Gesellschaft fur Heuristisch-Numerische Beratungssysteme mbH, in the field of heuristic-numeric systems for the distillation of close boiling and azeotropic mixtures. The described software TEAGPERT designs such separation processes by using heuristic rules for the selection and the design of flowsheet elements as well as numeric programs and databases. Based on an analysis of the boiling behavior of tie mixture TEAGPERT selects thermodynamically proven separation units. In addition, a first mass balance is calculated which serves as a starting point for further detailed simulations with common flowsheet simulators. The paper describes in detail the use of the software for the prediction of separating cuts. In addition, a design procedure for heteroazeotropic distillation processes with mass agents is presented.