A fibrillar polyaniline/diatomite composite was prepared by one-step in situ polymerization of aniline in the dispersed system of diatomite, and was characterized via Fourier-transform infrared spectra (Fr-IR), UV-vis-NIR spectra, wide-angle X-ray diffraction (WXRD), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM), as well as conductivity. Morphology of the composite is uniform nanofibers, which the diameters of nanofibers are about 50-80 nm. The conductivity of polyaniline/diatornite composite contained 28% polyaniline is 0.29 S cm(-1) at 25 T, and temperature of thermal degradation has reached 493 degrees C in air. The composite has potential commercial applications as fillers for electromagnetic shielding materials and conductive coatings. (c) 2004 Elsevier B.V. All rights reserved.