Ethylene propylene rubber-clay nanocomposites (EPR-CNs) were prepared by melt-compounding maleic anhydride modified EPR (EPR-MA) with organophilic clay, and their properties were examined. Silicate layers of organophilic clay were found to exfoliate and homogeneously disperse into the nanometer level in the nanocomposites by transmission electron microscopy observation. EPR-CNs exhibited higher tensile moduli compared to EPR-MA and composites containing conventional fillers such as carbon black, talc. The storage moduli of EPR-CNs were also higher than those of EPR-MA and the conventional composites. Creep resistances of EPR-CNs were much improved compared for EPR-MA. Degree of swelling in hexadecane was remarkably restricted. Improvement of these properties is caused because dispersed silicate layers have much large interface with the EPR matrix and are thought to strongly restrain the EPR polymer chains. Nanocomposite technology using small amount of silicate layers is useful to improve properties of thermoplastic elastomer. Various kinds of thermoplastic elastomers are expected to be produced by loading of silicate layers with or without conventional fillers. (C) 2004 Wiley Periodicals, Inc.