Polymer microspheres were synthesized by dispersion copolymerization of divinylbenzene (DVB) with vinylbenzyl-terminated poly (t-butyl methacrylate) (PBMA) macromonomers in nonaqueous media (methanol and acetonitrile). The particle diameter increased gradually with an increase of the DVB concentration in methanol or acetonitrile. The particle size distribution was very narrow. PBMA macromonomers acted not only as a comonomer but also as a stabilizer. The particle diameters obtained in acetonitrile were smaller than those obtained in methanol. Thus, we observed a tendency in which the more soluble for PBMA macromonomer the media became, the smaller the particle size became.