The experiments were carried out to high conversion levels at 50°C with an initiator concentration of 0.071 moi!L (2,2'-azo-(bis)isobutyronitrile) and a chain transfer agent concentration of 0.0058 mol/L (n-dodecyl mercaptan). For each experiment, samples were analyzed for conversion by gravimetry and for composition by proton nuclear magnetic resonance ( 1 H-NMR) spectroscopy.The overall rate of polymerization was greatly influenced by the amount of BA in the feed and to a lesser degree by the ratio of acrylic monomers (BA + MMA) to V Ac in the feed . Using reactivity ratios previously estimated from low conversion bulk copolymerization experiments, the bulk terpolymerization composition data were well predicted by terminal model kinetics up to high conversion levels.