Melt-state and solid state mechanical properties and thermal stability of polylactide layered silicate nanocomposites elaborated by melt intercalation were studied as a function of clay content. Wide angle X-ray scattering results, transmission electron microscopy observations, and rheological measurements indicated that the clay was finely distributed in the polylactide matrix. Contrary to nonlinear mechanical properties, thermal and linear mechanical properties were shown to increase with increasing clay fraction. The nanoindentation measurements confirm the significant increase of linear mechanical properties previously observed by tensile tests. The good correlation of linear mechanical properties at the macrometric and nano-metric scales is explained by the high dispersion degree of the nanofiller in the biodegradable polymer matrix. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116: 1357-1365,2010