Nickel-tungsten alloys were electrodeposited on stationary working electrodes from a nickel sulfate, sodium tungstate, and tri-sodium citrate-based bath under different operating conditions. The microstructure of the deposits was studied by X-ray diffraction, the morphology by scanning electron microscopy and atomic force microscopy, and the approximate composition by energy dispersive spectroscopy. Different Ni-W phases, either amorphous or crystalline, were associated with different plating conditions. A body-centered tetragonal Ni4W phase was formed only at high temperatures and low current density. This is the first time that the formation of this phase by electroplating was observed repeatedly. (C) 2005 The Electrochemical Society.