The first stages of nickel electrodeposition on amorphous carbon and polycrystalline silver substrates have been studied under galvanostatic conditions. An island growth mode is observed on the two types of substrate. For equivalent conditions the cluster density is higher on silver substrates than on carbon substrates. Dissolution of some nickel clusters is observed a short time after the onset of electrolysis on carbon substrates. This is confirmed by the evolution of the current efficiency and the evolution of the metal surface cluster density as a function of the quantity of electricity.