The RITP (reverse iodine transfer polymerization)-dispersion polymerization of methyl methacrylate (MMA) was conducted and the molecular weight and SEM images of them were investigated to propose the mechanism of the formation of surface morphology in crosslinked polymers. The morphology of the crosslinked particles varied depending on the sorts and contents of the crosslinking agents and iodine. As the iodine content increased under the same content of the crosslinking agent, the average molecular weight of the polymers [uncrosslinked portion of the polymers] decreased and the surface roughness simultaneously reduced. On the other hand, as the contents of the crosslinking agent increased, the molecular weight of polymers reduced and the surface morphology changed from smooth to rough in the absence of iodine. On the other hand, was the molecular weight was barely changed and the solubility increased upon iodine. Thus the mechanism of the formation of crosslinked polymers in the RITP-dispersion polymerization was proposed as the following; when crosslinking agent and iodine were simultaneously involved, the low molecular weight of polymers were first formed due to the effect of iodine and then the crosslinking was taking place, resulting in that iodine was a critical factor in controlling the molecular weight, particle size, solubility and the surface morphology in the crosslinked polymer particles. (C) 2011 Elsevier Ltd. All rights reserved.