Dispersion polymerization in polar organic media is a heterogeneous polymerization process that combines solution polymerization in the continuous phase with microbulk polymerization in the disperse particle phase. The relative prevalence of the two polymerization modes is dependent on a number of reaction variables. A mechanistic picture of dispersion polymerization during the particle growth phase is presented and mathematical models of the rate of polymerization and particle growth during seeded batch and continuous polymerization is developed.