Exact analytical expressions are derived for the particle size and molecular weight distributions formed in microemulsion polymerization. These results follow directly from a mechanistic model of the polymerization reaction which has been quantitatively validated in kinetic studies. An additional mild assumption regarding radical exit is necessary, and it is assumed there is no particle coalescence. The theoretical distributions are used to simulate results from quasielastic light scattering and gel permeation chomatography. The shape of the predicted particle size distributions and the effect of initiator concentration, microemulsion composition, and conversion on the average particle size all agree with experiment.