Polyaniline (PANI) salts doped with inorganic acids (HCl, H2SO4 and H3PO4) were directly synthesized by using solid-state polymerization method. The FTIR spectra, UV-vis absorption spectra and X-ray diffraction patterns were used to characterize the molecular structures of the PANI salts. Voltammetric study was done to investigate the electrochemical behaviors of all these PANI salts. The PANI salts were affected by varying the protonation media (HCl, H2SO4 and H3PO4). The FTIR and UV-vis absorption spectra revealed that all PANI salts contained the conducting emeraldine salt phase at different oxidation state. The crystallinity of PANI doped with HCl was better than those doped with H2SO4 and H3PO4. The conductivity of the PANI doped with HCl is the highest among the inorganic acid doped PANI. (C) 2004 Elsevier B.V. All rights reserved.