Aniline has been electropolymerized in acetic acid at a controlled potential of 1.1 V (vs. SCE). The polymer obtained from this system was undoped-like and soluble in many organic solvents such as acetic acid, N-methyl-2-pyrrolidone (NMP), acetonitrile, tetrahydrofuran, methanol, alcohol and acetone. Its electrochemical behavior and structure have been examined by cyclic voltammetry and UV-visible and FT-infrared spectroscopies. The experimental results indicated the polymer has a short and branched structure.