The effect of the solvent used in the chemical polymerization of pyrrole on the electrochemical pseudo-capacitance properties of the material is investigated by means of cyclic voltammetry. Electro-conducting polypyrroles (PPy) are prepared in the presence of various solutions such as H2O, diethyl ether, and acetonitrile (ACN). The PPy powder prepared in H2O exhibits the largest capacitance value, approximately 355 F g(-1), in ACN solution containing 1 M tetraethylammonium tetrafluoroborate (TEABF(4)). This dependency on solvent is directly related to the surface roughness of PPy powder. (C) 2003 Elsevier B.V. All rights reserved.