The synthesis and characterization of latex particles consisting of a poly(styrene) (PS) core and a shell of linear poly(acrylic acid) (PAA) chains are described. The particles have been synthesized by photoemulsion polymerization of acrylic acid on PS core particles containing a thin shell of the photoinitiator 2-[p-(2-hydroxy-2-methylpropiophenone)]-glycol-methacrylate (HMEM). The particles thus obtained have a defined core-shell morphology with a narrow size distribution. The dependence of the hydrodynamic radius of the fully dissociated PAA chains on the ionic strength is in qualitative accord with recent theoretical predictions.