Aqueous electropolymerization of thiophene and 3-methylthiophene was accomplished on β-PbO2 electrodes. Poly 3-methylthiophene films were also formed on α-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 β-PbO2 compared to the platinum electrode in pure acetonitrile, whereas this limit was lowered only by about 200 mV on the α-PbO2 electrode. In the case of 3-methylthiophene, the upper potential limit was decreased to 1.1 V vs. Ag|AgCl on the β-PbO2 electrode and this lower limit was found to be 1.3 V vs. Ag|AgCl on the α-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.