Optimization of a semicontinuous emulsion polymerization reaction is carried out using a mathematical model derived from first principles to represent the process. Iterative Dynamic Programming (IDP), being a straightforward procedure that allows the implementation of optimization constraints, is an attractive tool to optimize highly complex and nonlinear equation systems such as those that are used to represent the emulsion polymerization processes. In order to minimize the reaction time of a semicontinuous reaction, time intervals with varying lengths were used allowing the establishment of the optimal operation conditions where the final time is not specified. The optimization procedure is applied to two emulsion polymerization systems: (a) butyl acrylate/vinyl acetate copolymerization with controlled composition; (b) vinyl acetate homopolymerization with specified molecular weight. Results show that significant reductions of reaction time are possible and that their extent depends on the reactor's heat removal capacity and on the formulated constraints. (C) 2003 Published by Elsevier Science Ltd.