The effect of process variables such as nozzle size, flow-rate of dispersed phase, inter-electrode distance, and presence of an acid acceptor and a thickening agent in the dispersed phase, on the production and size distribution of nylon 6-10 microcapsules prepared by interfacial polymerization in a high-voltage electric field was studied. Factors which increased the intensity of the electrostatic forces acting upon the droplets formed, such as increasing nozzle diameter at constant aqueous phase flow-rate and decreasing inter-electrode distance, were found to decrease the capsule size while those which enhanced the availability of the aqueous phase monomer for the polymerization reaction, such as the addition of an acid acceptor and a thickening agent, resulted in an increase in the average size of the capsules obtained. Free flowing capsules and a reduction in the rate of diacid chloride hydrolysis during the process were also obtained with increasing concentration of the thickening agent in the aqueous phase.