This article describes the copolymerization of acrylamide with styrene in oil-in-water microemulsion, using dodecyl betaine as emulsifier and alpha-hydroxy-alpha,alpha-dimethyl acetophenone or alpha,alpha-dimethoxy-phenyl acetophenone as photoinitiator. Results indicated that the photoinitiation of polymerization occurs at the interface between the oil phase and the water phase and that the polymerization occurs in the microemulsion droplet. Particle size increased with increasing polymerization time. The copolymer chain consisted of isolated acrylamide units randomly distributed among styrene groups.