The intention of this paper is the theoretical analysis and optimization of preferential crystallization of enantiomers performed simultaneously in two batch crystallizers which are coupled. An exchange of the liquid phases may increase the overall crystallization kinetics and that might lead to a higher productivity. In this study, the amino acid threonine dissolved in water was used as a model system. Taking experimentally estimated parameters describing the crystallization thermodynamics as well as kinetics into consideration, a simplified mathematical description based on population balance model was established for the simulation of the time changes of liquid phase composition during the preferential crystallization process. Based on this simplified model the above mentioned crystallizer configurations has been optimized and investigated concerning the maximum attainable productivity. (C) 2007 Elsevier Ltd. All rights reserved.