A new polymer of o-tolidine was synthesized by chemical and electrochemical methods from its aqueous solutions in 1M HCl Chemical oxidative polymerization was performed using ammonium peroxydisulfate as an oxidant. Electrochemical polymerization was carried out using two steps which were successively repeated in a continual process: first, holding the working platinum electrode under a constant anodic potential of +1.6 V, and second, the voltammetric cycle between +0.3 and +1.6 V. During this procedure a polymeric film was formed on the working electrode. Polymerization of o-tolidine was exactly proved by gel permeation chromatography evidencing the chains of molar masses in the range of 1000 - 12600 g mol(-1). The structure of poly(o-tolidines) obtained by both chemical and electrochemical procedures was studied by IR spectroscopy. Coupling pathway N-C during polymerization, existence of quinonoid rings and hydrogen bonding involving NH group in polymeric products are revealed by IR spectroscopic analysis. The mechanism of o-tolidine oxidative polymerization is proposed.