In the field of the electrocoating of cars and trucks (electrodeposition of paint applied by an electrical field) the industrial application has preceded full theoritical comprehension of the phenomena involved. In (act, the explanation of the complex phenomena of the electrodeposition process has been achieved (although not completely) only a few years after its industrial diffusion. This is particularly true for cathodic electrocoating. Vary little can be said at present about the correlation between the technological properties of the paint and the optimum composition and parameters of the paint bath. Also, the influence of the variation occurring in the paint composition (oxidation, ageing, preferential deposition, etc.) has to be investigated. In this paper the application of high performance liquid chromatographic (HPLC) techniques (on bonded-phase columns) working in direct, reversed, and ion-paired reversed-phase modes is described. The satisfactory results achieved via HPLC allowed the authors to obtain a polymer fingerprint (oligomeric distribution, impurities, etc.) and to devise a simple way to begin a systematic control of the aging of electropainting baths and quality control of the industrial manufacturing of electrophoretic polymers.