A new type of computer-based consulting system for the choice of chemical reactors during the first step of process design is presented. Because neither expert systems nor numerical calculations alone are able to solve the problem of proper reactor choice, a new type of computer program has been developed, the heuristic-numeric consulting system READPERT (Reaktor Entwicklungs-Auswahl und Design Expertensystem, i.e. Reactor Development, Selection and Design Expert System). On the one hand, it uses expert system technology and knowledge representation forms, such as rules and frames, and on the other hand numerical calculations, as a part of a wide range of chemical engineering tools. In this way advice for the design of a chemical reactor can be given even at an early stage of process design. READPERT can be used as a stand-alone system as well as part of PROSYN (Process Synthesis), a range of cooperating distributed heuristic-numeric systems, for computed-aided process synthesis.