Ethylene-propylene-diene rubber (EPDM)/ organomontmorillonite (OMMT) nanocomposites were prepared with a maleic anhydride grafted EPDM oligomer as a compatibilizer via melt intercalation. X-ray diffraction and transmission electron microscopy indicated that the silicate layers of OMMT were exfoliated and dispersed uniformly as a few monolayers in nanocomposites. The change in the crystallization behavior of the nanocomposites was examined. The nanocomposites exhibited great improvements in the tensile strength and tensile modulus. The incorporation of OMMT gave rise to a considerable reduction of tan delta and an increase in the storage modulus. Moreover, the solvent resistance of the nanocomposites increased remarkably. (C) 2004 Wiley Periodicals, Inc.