Dispersions of micron-sized styrene droplets in water were produced by straight through microchannel arrays. The monomer droplets have been polymerized by suspension polymerization using an initiator system, which was only oil soluble. A significant amount of submicron particles was formed by secondary nucleation. The side reaction was emulsion polymerization, which was confirmed by the molecular weight distribution of the reaction product. Suppression of secondary nucleation was only partially possible by using the water soluble inhibitor NaNO2. Increasing the monomer to water ratio before polymerization resulted in less emulsion polymerization. Molecular weight was found to be strongly dependent on the initiator concentration as well as on the inhibitor concentration. It was demonstrated that polymer particles with a diameter of about 10¿µm can be produced using emulsification of the monomer by microchannel arrays prior to polymerization.