Many mechanistic aspects of emulsion polymerization processes remain unclear, despite their industrial importance. Thus, for example, several different mechanisms have been postulated for the formation of latex particles (for recent reviews, see Refs. 1 and 2), and for the capture of free radicals by these latex particles [3,4], The origin of such problems is that there are a large number of mechanistic processes which may reasonably be assumed to be significant in the formation and growth of latex particles. Any theoretical model used for data interpretation with a view to extracting specific mechanistic information must perforce contain many rate parameters which are either peculiar to an emulsion polymerization system or whose values, while obtainable in principle from different experiments, are subject to considerable uncertainty. Given limited experimental data, therefore, it is frequently possible to find “evidence” to support several mutually incompatible mechanisms for the various steps involved.