Emulsion polymerization of vinyl acetate was performed in a system of two continuous stirred tank reactors in series to observe dynamic chemical processes. Monomer and an aqueous solution of initiator and emulsifier were separately and continuously fed into the first reactor. The concentration of emulsifier was considerably lower than the critical micelle concentration. The reacting latex solution discharged from the first reactor was fed into the second reactor. The mean residence time and the speed of the rotational impeller were varied as control parameters. After a transitional period, a steady state of almost constant monomer conversion was attained. Even while this steady state was maintained, the particle-size distribution varied periodically. The mean diameter of latex particles also oscillated over time. A broader distribution was obtained in the second reactor, where, from a certain sampling time, a bimodal particle-size distribution was observed. These results indicate that the aggregation process predominates over the reaction process in the second reactor. It was also found that oscillatory behavior can be controlled by adjusting the rotational speed of the impeller and the mean residence time, with the former influencing the amplitude of oscillation and the latter the period thereof.