Grafting of polystyrene from narrow disperse polymer particles by surface-initiated atom transfer radical polymerization was investigated. Poly(DVB80) particles prepared by precipitation polymerization were used as starting particles. Their residual surface vinyl groups were hydrochlorinated to form chloroethylbenzene initiating sites for subsequent ATRP of styrene using CuBr/2bipy as catalyst system. Polystyrene was found grafted not only from the particle surfaces but also from within a thin shell layer, leading to particles size increases from 2.96 to 3.07 mum. The surface layer of polystyrene improved colloidal stability and facilitated formation of colloidal arrays. Block copolymers of poly(styrene-b-4-methylstyrene) were grown from the particles, and the living nature of surface-initiated ATRP is discussed.