Synthesis and characterization of polymer nanocomposites consisting of diglycidyl ether of bisphenol-A with inorganic as well as organically modified nanosized clay fillers, for example, vermiculites and montmorillonite, obtained from trade, are studied. Confirmations of intercalation and exfoliation characteristics of these fillers into the cured epoxy resin matrix have been investigated by wide angle X-ray diffraction studies. Scanning electron microscopy and atomic force microscopy techniques have been adopted to assess the nature of filler dispersion, size of the agglomerates, and the polymer-filler adhesion. While significant improvement in the mechanical properties (i.e., tensile, flexural strength, and modulus) has been observed, the thermo-oxidative stability of the composites measured by thermogravimetric analysis showed only marginal improvement. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012