A starved feed reactor (SFR) is a semibatch polymerization reactor in which initiator and monomer are fed slowly into a fixed amount of solvent. The polymerization is carried out isothermally at elevated temperatures. The added initiator decomposes instantaneously, and the added monomer polymerizes immediately. The monomer concentration in the SFR is very low, ideally approaching zero. The reactor is in a starved status for reactants. The molecular weight of the product polymer can be effectively controlled by the feed ratio of monomer to initiator. This article presents a study on the kinetics of NBMA polymerization in an SFR. The model parameters were regressed with the experimental data. Although the mass fraction of polymer in the SFR was high (higher than 50%), viscosity was not high and the "gel effect" was weak because of the low molecular weight of the products. It was found that the termination rate constant is a power function of polymer concentration, and the lumped rate constant, k(p)/(k(t)(0))(1/2), can be modeled by the Arrhenius equation. The initiator efficiency, f, remained constant at a temperature less than 120 degreesC, and increased with the temperature increasing at temperatures greater 120 degreesC. The other parameters remained constant in the experiment range.