Iron silicide was prepared by electron beam deposition of 90 nm iron on hydrogenated amorphous silicon films (a-Si:H) of 500 nm thickness and subsequent annealing. The influence of hydrogen was studied by preparing a-Si:H films with different hydrogen contents ranging from 1.5 to 13 at.%. This was achieved by choosing different substrate temperatures between 150 and 350 degrees C for the glow discharge deposition of the amorphous films on crystalline silicon substrates. For comparison iron was also deposited directly on crystalline silicon. Auger profiling revealed disilicide formation on crystalline silicon and monosilicide formation on amorphous silicon after annealing at 600 degrees C for 2 h. Post processing of the Auger data by neural pattern recognition confirmed this result. No influence of the different hydrogen contents could be found for the amorphous silicon samples. For these samples a blistering effect was observed which increased with hydrogen content. This was investigated by hydrogen effusion, scanning electron microscopy, micro-Raman scattering, X-ray photoelectron spectroscopy and thickness measurements.