The chemical oxidative polymerization of diphenylamine-4-sulfonate (DPASA) was carried out in aqueous and 0.5 M H2SO4 solutions using potassium peroxodisulfate (PDS) as an oxidant. The course of polymerization was followed by UV-visible spectroscopy. The absorbances corresponding to the;intermediate and the polymer were followed for different concentrations of DPASA and PDS and at different times of polymerization. The medium was found to be homogeneous and became green colored. The rate of polymerization (R-p) was determined for various conditions. The observed dependences of DPASA and PDS on R-p were used to deduce a rate equation for the polymerization of DPASA. The rate constant for the formation of poly(diphenylamine-4-sulfonic acid), PDPASA, was estimated. Spectroelectrochemical studies were carried out using indium tin oxide as the working electrode to follow the course of polymerization under electro-oxidative conditions. The polymer, PDPASA, was isolated from the reaction medium and characterized by H-1 NMR, FTIR spectroscopy, and thermogravimetric analysis.