Reversible addition-fragmentation transfer (RAF-F) polymerization of styrene (St) induced by gamma-ray irradiation has been successfully performed in miniemulsion using 2-phenylprop-2-yl phenyldithioacetate (PPPDTA) as chain-transfer agent (CTA). The results show that the polymerization bears all the characteristics of controlled/living free-radical polymerizations, Such as the number-average molecular weight (M,) increasing, linearly with monomer conversion, molecular weight (MW) being controlled and the molecular weight distribution (MWD) being narrow (polydispersity index (PDI) <= 1.30). Moreover. this system does not show a significant decrease in polymerization rate as compared to a conventional miniemulsion polymerization.