A PC based real-time simulator of the dynamic behaviour of non-linear MIMO (Multiple Input, Multiple Output) systems is presented. The strategy is developed in the time domain. Virtually all processes represented mathematically by sets of non-linear algebraic-differential equations can be described by the simulator. Exceptions, not yet found in our practice, may be cases of large number of ill-conditioned equations where the numerical strategies employed, albeit tested and robust, may experience difficulties. The User defines in very simple terms his own process (algebraic-differential) equations, control inputs, loads, measured variables and process parameters. The latter can be changed on-line during the simulation. Protocols for input/output are included for A/D, D/A and RS232 communications. Studies employing this simulator have been effectively conducted on penicillin and baker's yeast fed-batch fermentation, on sugar crystallization and on multiple-effect evaporation, among other systems.