Frontal polymerization is a method of manufacturing polymer via a self-propagating reaction wave. A mathematical model that describes both free-radical binary frontal polymerization and frontal copolymerization is presented. Linear stability of polymerization waves in the two monomer systems is studied. Parameters that are responsible for the loss of stability are identified, and stability boundaries in the parameter space are obtained. (C) 2004 Elsevier Ltd. All rights reserved.