MoO3/AC composite electrodes with various molybdenum oxide content were prepared using activated carbon with high surface area (S(BET)similar to1,900 m(2) g(-1)) by impregnation of activated carbon in methanolic solutions of MoCl5. The supercapacitive behavior of the composite material was characterized by cyclic voltammetry. An increase in capacitance compared to pristine carbon was observed in both alkaline and acidic electrolytes when the loading quantity was small (0.3-3.0 mass %). Enhancement of approximately 34% in capacitance was obtained with 1.4 mass % loading in 1.0 M NaOH electrolyte. The composite electrodes possessed excellent stability, with a capacitance decay of only 6% after 20,000 cycles.