Ruthenium oxide/ruthenocyanide (ruthenium oxide/hexacyanoruthenate, or mvRuO/RuCN) and iron(III) ruthenocyanide (ruthenium purple, or RP) hybrid films have been prepared using consecutive cyclic voltammetry, and the deposition process and the films' electrocatalytic properties in electrolytes containing Rb+ and Cs+ have been investigated. The hybrid ruthenium oxide/ruthenocyanide and RP films showed four obvious and separated redox couples with formal potentials between -0.2 and 1.0 V in monovalent cation aqueous solutions of RbNO3 or CsNO3. The cyclic voltammograms recorded the deposition of the hybrid films directly from the mixing of Ru3+, Fe3+, and Ru(CN)(6)(4-) ions in aqueous Rb+ or Cs+ cation solutions. An electrochemical quartz crystal microbalance and cyclic voltammetry were used to study the growth mechanism of the hybrid films. The electrochemical properties of the films indicate that the redox process was confined to the immobilized and mixed ruthenium oxide/ruthenocyanide and RP films. The electrocatalytic reduction properties of SO52- and S2O82- by the hybrid films were also determined, as well as the electrocatalytic properties of dopamine and epinephrine. The electrocatalytic reactions of the hybrid films were investigated using the rotating ring-disk electrode method. (C) 2004 The Electrochemical Society.