Aniline and several aniline derivatives were electropolymerized with two different electrolysis modes, potential sweep electrolysis and constant current electrolysis. The voltammetric and chronopotentiometric responses during the electropolymerization led to two polymerization mechanmisms: radical-coupling polymerization and incorporation-oxidation polymerization. The latter polymerization proceeds as follows. (1) In initial stage seed polymer with low molecular weight is electrodeposited on the electrode surface. (2) The seed polymer is electro-oxidized and cation radicals are generated in the seed polymer. (3) The cation radicals oxidize dissolved monomers and incorporate the oxidized monomers. This polymerization was found to give high conductive polyanilines. On the basis of the fact that the incorporation-oxidation polymerization obeyed Faraday`s law, the electron number of the polymerization reaction of aniline was analyzed coulometrically. The determined number implied that the polymeric backbone consisted mainly of benzenoid structures and that 0.36 anions were doped per an aniline unit. Aniline was electropolymerized using constant-potential electrolysis.The chronoampero-grams during the electropolymerization definitely had two different time dependences on the electrolytic current. During the initial stage, the current increased with the square of the electrolysis time, and then increased linearly with the time. Those results were intrinsically the same as those of the electrodeposition of metal ions. To determine the kinetic parameters, the electrolytic current during the polymerization was analysed on the basis of metal electro-deposition models developed by Fleishmann and Thirsk. The rate constant of the polymerization reaction was found to be directly proportional to the concentration of protons, to the concentration of anions and to the square of the concentration of aniline; also, the rate constant was formulated using the concentrations as well as the electrolysis potential and temperature. The concentration dependence of the rate constant led to the belief that the rate-determining reaction in the polymerization was the electro-oxidation of the dimer of aniline, p-aminodi-phenylamine.