Desorption of free radicals from particles can cause an emulsion polymerization system to deviate from Smith-Ewart case II kinetics. A mechanistic model has been developed to predict the effect of desorption of radicals from particles on the kinetics of semibatch emulsion polymerization of methyl acrylate under the monomer-starved condition. Experimental data available in the literature are used to assess the proposed kinetic model. The model predicts the experimental data reasonably well for a wide range of monomer feed rates. The rate of polymerization increases with an increase in the rate of monomer addition. The kinetic data are also useful in evaluating the desorption rate constant (K’(d)) for methyl acrylate. The best fitted value of K’(d) at 50 degrees C is 4 x 10(-12) cm(2)/s, which is in good agreement with the theoretical values predicted by desorption theory.