In this article we investigated the influence of various nanofilllers' aspect ratio, chemical nature, and organic modification on some selected nylon-6 properties, such as crystallinity, thermal and mechanical resistance, and fire behavior. Materials were prepared by twin-screw extrusion and characterized by means of scanning and transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, tensile tests, and cone calorimeter. Fillers characteristics were found to influence at different extents the material final properties. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1935-1948, 2009