An organic/inorganic hybrid nanocomposite membrane, poly(vinyl alcohol)/clay (PVAC), was prepared. The morphology of PVAC nanocomposite membranes were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and atomic force microscopy (AFM). The crystallinity and surface roughness increases with an increasing clay content in the PVAC nanocomposite membrane. Compared with the pure poly(vinyl alcohol) (PVA) membrane, the hybrid nanocomposite membrane (PVAC) shows an improvement in the thermal stability and the prevention of the water-soluble property. The oxygen permeability and the water-vapor permeation rate decreases with an increasing clay content (1-3 wt %) in the PVAC nanocomposite membranes. In addition, the effects of the clay content on the vapor-permeation performance of an aqueous ethanol solution through the PVAC nanocomposite membranes was also investigated. (C) 2003 Wiley Periodicals, Inc.