Nanocomposites based on isotactic polypropylene and montmorillonite were studied, investigating the polymorphism of the polymer, and examining the interaction between polypropylene and silicate. Wide angle X-ray diffraction (WAXD) was used to study the crystallization of the matrix, particularly the influence of additives and processing. Small angle X-ray scattering (SAXS) was employed to assess the lamellar morphology, estimating how silicate dispersion could affect this factor. Interaction between polymer and clay was quantified from WAXD and SAXS profiles; by the position and shape of the clay basal peaks, two different degrees of interaction were identified, characterized by a different affinity between the constituents. Observation of the samples' morphology by transmission electron microscopy (TEM) confirmed the results of X-ray diffraction methods. A fitting procedure was applied to SAXS profiles and the dimensions of the clay stratifications were estimated. These results were successfully compared with those drawn by application of Scherrer equation on (001) WAXD peaks. (c) 2005 Elsevier Ltd. All rights reserved.