A new method based on concepts of generalized species and equilibria, was applied to represent the thermodynamic distribution of americium species (including condensed phases) in an electrochemical system. Diagrams of the Predominance-zone, Existence-predominance and Pourbaix-type for the americium/ support electrolyte/water system were constructed. On the basis of these diagrams, the initial distribution of the species in the electrolyte and the deposition conditions were predicted when a current density was applied to a rotating disc electrode in steadystate. These results were related with the Hansen model for actinide electrodeposition.