By using the acoustic impedance method, storage (G') and loss moduli (G') have been determined for poly(pyrrole) films grown on the gold electrode of an electrochemical quartz crystal microbalance from aqueous LiClO4 and sodium tosylate solutions. At 10 MHz, for 0.3-0.4 mu m films G' = 6 x 10(6), G '' = 2 x 10(6) dyn/cm(2) for perchlorate and 2.5 x 10(8) and 1.1 x 10(8) dyn/cm(2) for tosylate ions were determined. Cycling in the corresponding monomer free solutions did not significantly change the properties of the perchlorate anion film, but decreased the moduli of the tosylate films to 6-8 x 10(7) dyn/cm(2). A slight increase of G during oxidation has been observed, i.e., the films are more stiff in the oxidized state. (c) 2006 Elsevier B.V. All rights reserved.