Electroless Ni-W-P films are compared to Ni-P with the same P/Ni ratio in order to study the role of tungsten in stabilizing the amorphous state. Differential scanning calorimetry and high-angle X-ray diffraction are used to study these films and compare their thermal stability and crystallization behavior. The results indicate that W inhibits nucleation of the Ni3P phase in Ni - W - P films, but has limited ability to suppress face-centered cubic Ni nucleation because W is soluble in Ni. (C) 2006 The Electrochemical Society.