The stability of the process for electrodeposition of CoPt alloys from ammonium citrate electrolytes containing [Pt(NO2)(2)( NH3)(2)](0) as the source of Pt was studied. Voltammetric monitoring of the anodic oxidation of the electrolyte and deposition of CoPt on the cathode showed the effect of the changes of the nature of the Pt complex on the performance of the plating bath. Anodic oxidation of the Pt complex was shown to involve mainly the oxidation of NO2- and to some extent NH3 ligands. The cathodic process is accompanied by reduction of free NO2-: The reduction of this anion in the bound form is highly inhibited. In contrast, its oxidation at the anode proceeds almost as readily in the bound form as that in the free form.