Exfoliated polymer/clay nanocomposites with high clay contents were facilely constructed by the vapor-phase assisted surface polymerization of methyl methacrylate (MMA) with montmorillonite premodified with a trimethylstearyl ammonium salt and a free radical initiator: 2,2'-azobis(isobutyronitrile). This method required only premodified MMT and vaporized vinyl monomer without any prehomogenizing and postpolymerization processes. The exfoliated structure of the nanocomposites, which was confirmed by X-ray diffraction analysis, was retained even after melt processing.