Low temperature reactions between Fe thin films and Si substrates have been studied. Iron films were deposited by electron beam evaporation onto [111] orientated Si substrates. An SiO2 capping layer was used to protect the Fe from oxidation during subsequent annealing. Samples were annealed at temperatures as high as 650 degrees C, for up to several hours. It has been shown that FeSi is the initial silicide to form, with 300 degrees C being the lowest formation temperature. Fe3Si forms after most of the Fe has been consumed, and forms as a separate phase from alpha-Fe and not through a disorder-order transformation. Microstructural evidence for nucleation controlled formation of beta-FeSi2 from FeSi has also been given.