n-Butyl methacrylate/styrene/n-butyl acrylate (BMA/ST/BA) high-temperature starved-feed solution semibatch copolymerization and terpolymerization experiments with varying monomer feed composition, final polymer content, monomer feed time, and reaction temperature were carried out. A comprehensive mechanistic terpolymerization model implemented in PREDICI includes methacrylate depropagation, acrylate backbiting, chain scission, and macromonomer propagation, as well as penultimate chain-growth and termination kinetics. The generality of the model was verified by comparison with terpolymerization data sets from two laboratories that demonstrate the impact of high-temperature secondary reactions on polymerization rate and polymer molecular weight. (C) 2010 American Institute of Chemical Engineers AIChE J, 57: 227-238, 2011