Pervaporation separation of chlorinated hydrocarbon/acetone mixtures has been investigated using nanoclay modified poly(ethylene-co-vinyl acetate) films. The results have been compared with the unfilled poly(ethyleneco-vinyl acetate) films. The nanoclay modified membranes were characterized by X-ray diffraction technique. The dispersion of layered silicates in the polymer matrix was analyzed using transmission electron microscopy. The nanoclay showed excellent dispersion in the polymer matrix. The effect of free volume on the pervaporation performance was investigated by positron annihilation lifetime spectroscopy. Poly(ethylene-co-vinyl acetate) nanocomposite membrane showed high selectivity because of the plateletlike morphology and high aspect ratio of layered silicates. The nano clay content and the swelling effects on pervaporation performance of nano composite membranes have been investigated in detail.