A user-friendly expert system was developed for the design of large scale continuous fermentation units for alcohol production. This expert system utilized an intensive rule-based program, with a knowledge base structured using both expert knowledge data and industrial practices, as well as computer simulations. The simulation algorithm was developed from mass and energy conservation of continuous multi-staged plants and kinetic equations representing the fermentation process by Saccharomyces cerevisiae. The kinetic parameters were adapted from industrial data, leading to a reliable mathematical model that represented the industrial process reasonably well. Since the system was designed for continuous processes with several stirred tanks connected in series, the optimal volume profile and number of stages were previously optimized. The system developed could be utilized either for the design of industrial plants or for the improvement and modernization of existing plants. This system was shown to be reliable since the difference between theoretical calculations and practical results was minimal.