The temperature dependence of saturation magnetization and the critical concentration xc corresponding to the onset of ferromagnetism were determined by ferromagnetic resonance on amorphous Fe x Ge 1−x thin films. In the concentration range 0,43<x<0,53 Ms follows a linear law as a function of temperature. The critical concentration is close to xc=0,4 and were deduced from the temperature dependence of magnetic moment and from Tc versus concentration. The results are discussed in term of a band model calculation and some peculiarities are explained by the amorphous structure corresponding to the concentration range studied.