Copolymers of halogenated styrenes and alpha-methylene-gamma-butyrolactone were synthesized in bulk via free radical initiation. The polymerizations, in most cases, proceeded rapidly to high conversion. The high conversions obtained necessitated the use of high conversion methods to calculate reactivity ratios. In all the copolymerizations the alpha-methylene-gamma-butyrolactone proved to be the more reactive monomer.