Aqueous electropolymerization of thiophene and 3-methylthiophene was accomplished on beta-PbO2 electrodes. Poly 3-methylthiophene films were also formed on alpha-PbO2 surfaces under acidic conditions. It was also determined that the upper potential limit for thiophene electropolymerization could be lowered by about 400 mV using beta-PbO2 compared to the platinum electrode in pure acetonitrile. whereas this limit was lowered only by about 200 mV on the alpha-PbO2 electrode. In the case of 3-methylthiophene, the tipper potential limit was decreased to 1.1 V vs. Ag\AgCl on the beta-PbO2, electrode and this lower limit was found to be 1.3 V vs. AQ\AgCl on the alpha-PbO2 electrode. It was also shown that the polymorphic composition and degrees of crystallinities of PbO2 films also influenced the extent of the electropolymerizations and the conductivity values. (C) 2004 Elsevier B.V. All rights reserved.