In this study, we investigated nanocomposites based on a natural biodegradable matrix. The polymer used was a natural potato starch, and the plasticizer was glycerol. A natural montmorillonite was studied and its loading in the matrix was 2.5 and 7.5 wt.%, respectively. Two film series were prepared by a solution/cast process: the first series was based on neat starch, and the second one was based on 20 wt.% glycerol plasticized starch. For all matrices, a mixture of intercalated and exfoliated structures was formed by the addition of montmorillonite. The thermal stability was not significantly affected by the presence of plasticizer and/or the addition of clays. The water sorption isotherms and water sorption kinetics were studied and modelled as a function of the composition of the films. The sorption mechanism was complex and resulted from a combination of different contributions involving the interactions between the plasticizer, the matrix and the nanoclays. The introduction of nanoclays led to decrease the oxygen permeability. This decrease seemed to be more efficient in presence of glycerol. (C) 2010 Elsevier B.V. All rights reserved.