The catalytic oxidation of pyrrole by the [(salen)(VOVV)-O-IV(salen)](3+) cation, which is formed on an electrode surface by the oxidation of [(salen)(VOVIV)-O-IV(salen)](2+), was examined by hydrodynamic voltammetry at a rotating glassy carbon disk electrode. The electron transfer rate constant for the cross-reaction [(salen)VOV(salen)](3+)/pyrrole was estimated to be 4 x 10(4) mol(-1) cm(3) s(-1). O-2-oxidation of the [(salen)VOV(salen)](+) cation gives rise to the catalysis for the O-2-oxidative polymerization of pyrrole. The polymerization was rate-determined by the reoxidation step of the catalyst by O-2.