Electrodeposition of pure nanocrystalline silver from a highly concentrated potassium iodide solution containing silver nitrate was described and discussed. The reversible electrode potential of the nanocrystalline material was measured versus polycrystalline silver. Grain growth of the deposit could be quantitatively determined from the decrease of the electrode potential with time. A parabolic law of growth is fulfilled, which gives the initial grain size of silver by extrapolation.