The polymerization of aniline (ANI) in aqueous medium in the presence of (NH4)(2)S2O8 and montmorillonite (MMT) resulted in the formation of a nanocomposite (PANI-MMT). The inclusion of PANI in the composite was confirmed by FTIR studies. The extent of PANI loading in the composite increased with ANI concentration at a fixed oxidant/MMT amount and with the oxidant amount at a fixed ANI and MMT weight, but decreased with an MMT amount at a fixed ANI and oxidant level. TGA revealed a higher stability for the PANI-MMT composite relative to PANI and confirmed a PANI loading of ca. 51% in the composite. The conductivity increased in all the cases. XRD analysis revealed no expansion of the d(001) spacing at 9.8 Angstrom, implying no intercalation of PANI within the MMT layers. Scanning electron micrography studies revealed interesting morphological features for the composites. Transmission electron micrography analysis revealed distinctive features and confirmed the formation of PANI-MMT composite particles of diameters in the 300- to 400-nm range. These composites could be obtained as stable colloids in the presence of poly (N-vinyl pyrrolidone) under selective conditions.