A new procedure for the electrosynthesis of polyaniline (PANI), based on the electropolymerization of aniline on a PANI-modified electrode, is proposed. The procedure is controlled by the chemical reaction between the aniline and the highest oxidized form of PANI. A spectroelectrochemical flow cell has been used to study the influence of the flow rate on this process, which has enabled direct observation of the autocatalytic mechanism. Unexpectedly, the hydrodynamic conditions do not seem to have an effect on the resulting polymer film. Similar results were obtained by carrying out the electropolymerization in nitric and perchloric acid.