A highly crosslinked, monodispersed polystyrene (PS) particle was prepared by the seeded semicontinuous dispersion polymerization using ready-made monodispersed PS seed particles. The effects of Styrene (in 2nd stage)/Styrene (in PS seed) ratio, addition point and feeding time of divinylbenzene (DVB), concentration of DVB and polymerization temperature on the particle size, size distribution and morphology of the resulting particles were investigated. Monodispersed PS particles with 15 wt% of the DVB were prepared at 1/1 in St/St ratio, In comparison, highly crosslinked monodispersed and smooth-surfaced PS particles containing up to 70 wt% of the DV-B were effectively prepared at 0/1.5% weight loss of the PS particles determined by TGA occurred from 353.3 to 389.6 degrees C and the degree of swellability in toluene decreased from 113 to 101% as the DVB concentration increased from 10 to 70 wt%, implying increased thermal stability and solvent resistance due to the increase of the cross-link density. This study demonstrates that the seeded semicontinuous process, primarily with the starved condition at the second stage, is an efficient way to obtain highly crosslinked, monodispersed PS particles. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115:3092-3102,2010