Polypyrrole films doped with molybdenum sulfide and tetrathiomolybdate anions, PPy-MoS42--MoS3 were prepared electrochemically from aqueous media and characterized in nonaqueous electrolytes consisting of acetonitrile as solvent and various perchlorate and tetrafluoroborate salts. The PPy-MoS42--MoS3 electrodes were initially soaked in acetonitrile in order to remove residual water that should be present in the film. The first cyclic voltammogram recorded in nonaqueous media showed a sharp cathodic wave when small cations were present in the electrolyte and also a large reduction current at the negative limit of the scan. The latter was attributed to the reduction of the residual water still present in die film after the soaking procedure in an organic solvent. Cyclic voltammetry and electrochemical quartz crystal microbalance results indicate mixed anionic and cationic transport. At the beginning of oxidation of the reduced PPy-MoS42--MoS3 electrode, cation expulsion dominates the charge transport process where anion ingress is dominating at the end of the oxidation cycle. The maximum low-frequency capacitance of about 95 F/cm(3) evaluated from the electrochemical impedance data is smaller than that commonly found for polypyrrole electrodes. The lower value was attributed to the presence of molybdenum trisulfide in the polypyrrole matrix which might block some redox sites of the polymer or lead to a less ordered polymeric structure.