Monodisperse, thermosensitive poly(N-ethyl methacrylamide) microgel particles were prepared by the batch precipitation/emulsion polymerization of water-soluble N-ethyl methacrylamide and the hydrophobic crosslinker ethylene glycol dimethacrylate initiated by potassium persulfate. Particular attention was paid to the effect of the crosslinker agent on the polymerization process (kinetics, conversion, and water-soluble oligomer content). Particles were characterized in terms of their size distribution and swelling capacity. A polymerization mechanism for the water-soluble monomer and non-water-soluble crosslinker is proposed and discussed on the basis of a combination of both emulsion and precipitation polymerization processes.