Conducting polyaniline-zirconium dioxide (PANI/ZiO(2)) composites were synthesized by 'in situ' deposition technique in the presence of hydrochloric acid (HCl) as dopant by adding the fine grade powder (average particle size of approximately 20 nm) of ZrO2 into the polymerization reaction mixture of aniline. The composites obtained were characterized by infrared spectra (IR) and X-ray diffraction (XRD) and thermogravimetric analysis (TGA). TG curves and DTG curves of the composites suggest that the thermal degradation process of PANI/ZrO2, composites proceeds in two-steps and the composites are more thermally stable than that of the pure PANT. The improvement in the thermal stability for the composites is attributed to the interaction between PANT and ZrO2, which restricts the thermal motion of PANT chains and shields the degradation of PANT in the composites. (C) 2005 Published by Elsevier B.V.