This study describes the effect of the clav content and its dispersion on deformation and fracture behavior of polyamide nanocomposites. Two nanocomposite systems, intercalated and exfoliated nanocomposites containing layered silicate, were compared. They were prepared by melt-compounding of polyamide with sodium montmorillonite or organophilized montmorillonite. It has been shown that while the exfoliated structure imparts to the nanocomposite higher stiffness and strength, the toughness is inferior to the intercalated nanocomposite. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 3752-3757, 2008