Polyaniline (PANI) is an organic semiconductor, which has attracted great attention in fundamental science and industries over the past decade due to its conductivity and electrochemical properties. The studies show that the three different synthetic methods produce PANI/Pt composites with different chemical compositions and electronic properties. The differences results from the overall oxidation state of the polymer and the interaction of nitrogen with the metallic Pt particles. The method of preparation influences the electrocatalytic oxidation of methanol and formic acid. Although, the electrochemically and chemically prepared PANI/Pt materials show some catalytic activity, they are not identical. PANI/Pt formed from the electrochemical reduction of PtCl 62- and PtCl42- shows enhanced catalytic activity relative to the other PANI/Pt composites. In addition, the catalytic activity of PANI/Pt prepared from the electrochemical reduction of PtCl42- is significantly enhanced relative to the PANI/Pt composite produced using PtCl62. (Abstract shortened by UMI.)