Precipitation polymerizations of 2-(diethylamino)ethyl methacrylate were carried out with ethylene glycol dimethacrylate and then trimethylolpropane trimethacrylate in acetonitrile to produce monodisperse, highly crosslinked microspheres. Poly(diethylaminoethyl methacrylate-co-trimethylolpropane trimethacrylate) [poly (DEAEMA-co-TRIM)] microspheres, in the range of 1.2-2.7 pm, were obtained with a total monomer concentration of 1 vol % with respect to the solvent, and they kept their identity with several polymerization parameters. When the total monomer concentration was increased further, individual particles lost their identity and aggregated. Poly (DEAEMA-co-TRIM) particles with a total monomer concentration of I vol % had more discrete spherical forms with smoother surfaces, whereas in the poly(diethylaminoethyl methacrylate-co-ethylene glycol dimethacrylate) system, sticky microspheres were obtained with a total monomer concentration of 2.1 vol%. Moreover, several polymerization parameters were investigated to control the physical properties of microspheres of poly(DEAEMA-co-TRIM) and to understand the nature of the precipitation polymerization. Thus, the average particle size increased frown 2.3 to 2.7 pin with an increased azobisisobutyronitrile concentration and then decreased to about 1.2 pm as the polymerization temperature was increased. All the microspheres produced under different polymerization conditions were found to be monodisperse (polydispersity index <0.1) with a narrow size distribution. (c) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 532-540, 2009