AbstractKinetic data on the emulsion polymerisation of styrene are discussed in the light of the Smith‐Ewart theory as modified by Gardon. It is shown that at least in the beginning of the reaction serious discrepances exist between experimental results and the theoretical concept. An electrolytic effect in cationic emulsifier systems was found. Emulsion polymerisation of vinyl acetate was investigated and the mechanism is discussed. The polymerisation of vinyl acetate in aqueous solution without added emulsifier begins as a true solution polymerisation but very soon changes to a suspension polymerisation. The latex particles formed are an order of magnitude larger than those obtained in the emulsion polymerisation and have a very narrow size distribution. There seems to be a very short period of particle formation in this syste