A series of poly(lactic acid) (PLA) nanocomposites containing from 1 up to 6 wt% of montmorillonite layered silicate were prepared by melt compounding followed by compression moulding. The morphology of the nanocomposites was investigated using transmission electron microscopy (TEM) and wide-angle X-ray diffraction (WAXD) and it was confirmed that the nanocomposite structures were intercalated. The average aspect ratio of the compounded nanoclay was found to be 50. Water vapour transmission rates (WVTR) through the films were measured at 38 degrees C and at a relative humidity of 90%. It was found that the measured values of Malt decreased with increasing nanoclay content up to a value of 5 wt% and the results gave good agreement with predictions from the Nielsen 'tortuous path' model. (c) 2013 Elsevier B.V. All rights reserved.