Organo-clay polymer nanocomposites offer improved material properties at very low filler loadings making them of immediate interest for application in body panels, claddings, and instrument panels. This improvement in properties requires that the organo-clay be well dispersed if not completely exfoliated. Conventionally, the dispersion and exfoliation of the organo-clay is evaluated using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Although both TEM and XRD data were found to correlate with flexural modulus of thermoplastic olefin nanocomposite materials, only TEM proved successful in quantifying the dispersion of the organo-clay in all nanocomposite materials (exfoliated, tactoid, or agglomerated tactoid). XRD was found to be capable of detecting exfoliation and intercalation but is limited because of clay dilution, preferred orientation, mixed-layering, and other peak broadening factors. (C) 2004 Wiley Periodicals, Inc.