Polyaniline ~PANI! has been studied as an active material for electrochemical capacitors. Polymerization of aniline to PANI has been carried out potentiodynamically on a stainless steel ~SS! substrate, instead of Pt-based substrates generally employed for this application. The PANI/SS electrodes have been evaluated by assemb領(lǐng) symmetrical capacitors in NaClO4 1 HClO4 mixed electrolyte and subjecting them to galvanostatic charge/discharge cycles between 0 and 0.75 V. The effect of substrate has been assessed by comparing the capacitance of PANI/SS and PANI/Pt electrodes. The capacitance of PANI/SS electrode is higher than that of PANI/Pt electrode by several times. The effect of sweep rate of potentiodynamic deposition of PANI/SS on capacitance has been investigated. At a power density of 0.5 kW kg21, a capacitance value of 815 F g21 of PANI is obtained for the deposition sweep rate of 200 mV s21. Increase in thickness of PANI on the SS substrate results in an increase in capacitance of PANI. This value of capacitance is the highest ever reported for any electrochemical capacitor material. Thus, in addition to a favorable economic aspect involved in using SS instead of Pt or Pt-based substrate, the advantage of higher capacitance of PANI has also been achieved.