Nanocomposites of chitosan and nanoclays (MMT-Na+ and Cloisite 3013) were prepared by solvent casting. The structural properties, thermal behaviors, and mechanical properties were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy, differential scanning calorimetry, thermogravimetry analyses, and an Instron universal testing machine. XRD and TEM results indicated that an exfoliated structure was formed with addition of small amounts of MMT-Na+ to the chitosan matrix. Intercalation along with some exfoliation occurred with up to 5 wt % MMT-Na+. Micro-scale composite (tactoids) formed when Cloisite 30B was added to the chitosan matrix. Surface roughness increased with addition of a small amount of clay. Tensile strength of a chitosan film was enhanced and elongation-at-break decreased with addition of clay into the chitosan matrix. Melt behavior and thermal stability did not change significantly with addition of clays. (c) 2005 Wiley Periodicals, Inc.