High energy resolved X-ray emission spectroscopy with variable electron beam excitation is applied for the study of solid-phase reactions in the Hf/(001)Si system at different annealing temperatures. It is found that annealing at 700 degrees C is accompanied by formation of HfSi. The HfSi? phase is formed at 780 degrees C, The formation of Hf silicides in depth is studied by measurements of Si L-2.3 X-ray emission valence spectra under different accelerating voltages. The data obtained by means of X-ray emission spectroscopy are compared with those obtained by means of Rutherford backscattering and electron-probe microanalysis techniques.