Substituted polyaniline, poly(o-toluidine), was synthesized by oxidative chemical polymerization method. Acetic, formic and oxalic acids were used as dopants during the polymerization process. Synthesized polymers were subjected to the spectroscopic and thermal analysis. Spectroscopic and thermal properties of the polymers are found to be affected by the type of the dopant ion used for doping purpose. Formation of different oxidation states of the polymer were confirmed by the spectroscopic (UV-Vis and FT-IR) analysis. Three step decomposition pattern similar to that of polyaniline are observed in the thermogram. The percentage yield as well as conductivity is found to be higher in formic acid doped polymer than that doped with acetic and oxalic acid. Increase in conductivity with increasing temperature was observed in all the polymers. (C) 2004 Published by Elsevier B.V.