The emulsion polymerization of styrene, activated by microwave irradiation and conductive heating, was modeled using the EMULPOLY® simulation package of the University of Waterloo. Microwave-activated initiation was modeled as adding a hypothetical second initiator. The kinetic rate constants and model parameters used in the simulation were taken from the simulator database, with the exception of the microwave activation constant, kir, and the efficiency, fr, of the hypothetical initiator. Model predictions of conversion, number- and weight-average molecular weights, for microwave- and thermally activated systems agreed well with the experimental data reported in the literature. The effects of microwave power supplied to the system on monomer conversion, molecular weight values and particle number were analyzed.