We present a facile access route to hydroxy-functional narrow disperse microspheres of well-defined grafting density (GD). Ethylene oxide has been grafted from highly crosslinked poly(divinyl benzene) microspheres by anionic ring-opening polymerization using sec-butyllithium as activator together with the phosphazene base t-BuP4. Initially, core microspheres have been prepared by precipitation polymerization utilizing divinyl benzene (DVB, 80 wt.-%). The grafting of poly(ethylene oxide) (PEO) from the surface resulted in the formation of functional core-shell microspheres with hydroxy-terminal end groups. The number average particle diameter of the grafted microspheres was 3.6 mu m and the particle weight increased by 5.7%. The microspheres were characterized by SEM, FT-IR spectroscopy, elemental analysis, and fluorescence microscopy. The surface GD (determined via two methods) was 1.65 +/- 0.06 and 2.09 +/- 0.08 chains.nm(-2), respectively.