Blown PA6-based nanocomposite films were prepared and studied for a wide range of montmorillonite content (from 0 to 13 wt% of inorganic layers). The crystalline morphology of the polyamide matrix was shown to be only slightly dependent on the filler loading, allowing to discuss the nanocomposites water transport properties as a function of the filler content and dispersion state. The water vapour sorption mechanism of the polymer phase was found to be independent on the filler amount. In the range of activity between 0 and 0.9, the nanoclays behaved as impermeable fillers and the water barrier properties of the nanocomposite films were improved in comparison with the neat PA6 film thanks to a tortuosity effect. At higher activity, e.g. in liquid water, the clay aggregates were able to swell within the matrix, as this one was itself highly swollen. Hence, the equilibrium water uptake and the water permeability of the nanocomposite films highly depended at this water activity, on the clay dispersion state. (C) 2008 Elsevier B.V. All rights reserved.