A multivariable constrained model predictive control was formulated and implemented to control online an emulsion terpolymerisation process. A generic multilayer control architecture for real-time implementation of optimal control policies for particulate processes was also developed. The methodology was implemented within a multi-tiered software environment for real-time implementation of model-based control strategies. A full mechanistic dynamic model for emulsion terpolymerisation, developed in our previous work, is used as a real-time soft-sensor and incorporated within the MPC strategy. The simultaneous control of key polymer properties such as the particle size distribution (PSD), average molecular weight (Mn) and terpolymer composition were investigated using case studies involving manipulation of flow rates of monomers (styrene, MMA, MA), surfactant and initiator, and the reactor temperature. Although some offsets were observed with a degree of model mismatch, the experimental results agreed well with predictions. (C) 2009 Elsevier Ltd. All rights reserved.