The thermodynamic simulation under the kinetic control state indicates that 1.77-mu m-sized monodispersed polystyrene (PS) particles can absorb 500 times the amount of the styrene monomer with keeping the monodispersity by the "dynamic swelling method" (DSM) which the authors proposed in 1991. Actually, about 14.1-mu m-sized monodispersed styrene-swollen PS particles in which PS seed particles absorbed 500 times the amount of styrene monomer were successfully prepared utilizing DSM. By one-step seeded polymerization for the dispersion of the swollen particles at 30 degrees C for 48 h with the 2,2＇-azobis(4-methoxy-2,4-dimethyl valeronitrile) initiator, 13.1-mu m-sized monodispersed PS particles were produced.