Electrochemically synthetized poly(o-toluidine) (POT) films were studied in 3.7 M HClO4 and 1 M HClO4 solutions. The optical indices n- i k, at 0.1 V and 0.6 V were calculated in the 405 nm < lambda < 580 nm range. Undoped films show an increase in thickness, d, of about 10% related to the doped state. The decrease of the electrolyte concentration yield a decrease in "d" and an increase in "n", as compared to a more compact structure of the him. The pseudacapacitive charge, Q, corresponding to the reduction of the doped state, was measured as a function of the thickness.