Electronically conducting polypyrrole doped with heteropolytungstate anions [SiW12O40]4-, and [P2W18O62]6- were synthesized by electrochemical polymerization. The polymers exhibited reversible redox properties inherent to the heteropolyanions in addition to those of the polypyrrole moiety. The anions were retained in the polymer matrix without being ion-exchanged after repeated potential cycles in electrolyte solutions containing no heteropolyanions. Charge compensation on reduction was accomplished by cation insertion instead of releasing the anions. The spin density of the polymer with [P2W18O62]6- was small, indicating bipolaron formation accelerated by the polyanions. The polymers showed potentially useful properties.