Poly(vinyl chloride) based nanocomposites were prepared by blending with organically modified bentonite particles at three different temperatures 160 degrees C, 170 degrees C, 180 degrees C to compare the temperature effect on the morphology of the composites. The unmodified bentonite was also used as the filler material to prepare poly(vinyl chloride)/unmodified bentonite for comparison. The thermal properties of the samples prepared in this work were examined by differential scanning calorimetery and thermal gravimetric analysis. The results of differential scanning calorimetery showed the existence of the single glass transition temperature for all compositions and in comparison with pristine poly(vinyl chloride) the composites made out to be higher glass transition temperatures. The thermal degradation temperature of the composites also increased up to 60 degrees C in comparison with pristine poly(vinyl chloride). The dispersion and interfacial compatibility of bentonite in poly(vinyl chloride) matrix was characterized by scanning electron microscope.