The performance of a newly designed, polyaniline-activated carbon, hybrid electrochemical capacitor is evaluated. The capacitor is prepared by using polyaniline as a positive electrode and activated carbon as a negative electrode. From a constant charge-discharge test, a specific capacitance of 380 F g(-1) is obtained. The cycling behaviour of the hybrid electrochemical capacitor is examined in a two-electrode cell by means of cyclic voltammetry. The cycle-life is 4000 cycles. Values for the specific energy and specific power of 18 Wh kg(-1) and 1.25 kW kg(-1), respectively, are demonstrated for a cell voltage between 1 and 1.6 V. (C) 2002 Elsevier Science B.V. All rights reserved.