Polymeric microspheres were prepared from a Merrifield resin via nitroxide-mediated radical polymerization. Polystyrene, poly(acetoxystyrene), and poly[styrene-b-(methyl methacrylate-co-styrene)], poly(acetoxystyrene-b-styrene), and poly(styrene-co-2-hydroxyethyl methacrylate) copolymers were demonstrated to graft onto 2,2,6,6-tetramethyl-l-piperidinyloxy nitroxide bound Merrifield resins. The polymerization control was enhanced both on the surface and in solution by the addition of sacrificial nitroxide. The significant increase in the particle diameter (more than a fivefold volume increase for polystyrene brushes) showed that polymer growth was not only on the surface but also within the particles, and this diameter increase could be adjusted through changes in the molecular weight of the polymers. The microspheres were characterized by elemental analysis, IR spectroscopy, particle size analysis, and optical microscopy. (c) 2005 Wiley Periodicals, Inc.