In situ resistivity measurements have been used to determine the kinetics of crystal growth of co-evaporated NiSix films. Samples with various heat treatments have been examined with X-ray diffaction to determine the phases growing. It is found that all the films contain crystallites as deposited and that NiSi2 or Ni2Si grow in most of them. The variations in activation energy and the "mode of transformation" with composition are explained. © 1990.