Isobutylene isoprene rubber (IIR)-clay nanocomposites have been prepared successfully by melt intercalation with maleic anhydride-grafted IIR (Ma-g-IIR) and organophilic clay. In IIR-clay nanocomposites, the silicate layers of the clay were exfoliated and dispersed into the monolayer. The nanocomposites exhibited greater gas barrier properties compared with those of Ma-g-IIR. When 15 phr clay was added, gas barrier properties were 2.5 times greater than those of Ma-g-IIR. (c) 2005 Wiley Periodicals, Inc.