Batch polymerization experiments are combined with simulations to investigate the depropagation behavior of butyl methacrylate (BMA). Experiments carried out between 110 and 145 degrees C and polymer contents between 9 and 34 wt %, including experiments conducted with added polymer, indicate that equilibrium monomer concentration ([M](eq)) varies not only with temperature but also with polymer content. An extended Predici model provides a good fit to the monomer concentration and polymer molecular weight profiles, with the simulated monomer profiles at 132 and 145 degrees C sensitive to small changes in the depropagation activation energy. Thus, these data provide a better estimate of depropagation kinetics than those measured by the pulsed-laser polymerization/size-exclusion chromatography method. The entire data set is well-represented by [M](eq) (mol center dot L-1) = 1.76 x 10(6)(1 - 0.778x(wp)) exp(-6240/T), in which x(wp) represents the weight fraction of polymer in the system.