This Technical Report describes a X-ray fluorescence (XRF) spectrometric method for the determination of Si and Al contents in ferro-silicon materials. The method is applicable to: - Si contents between 40 % and 90 %; - Al contents between 0,5 % and 6 %. The correction of the spectrometric measurement from spectral interferences on the analytical lines used is essential. This Technical Report is valid for the analytical lines: - Si Kα 7.126 (for element contents between 45 % and 90 %); - Al Kα 8.339 (for element contents between 0,8 % and 6 %); - Fe Kα 1.937 (for element contents between 10 % and 58 %). NOTE For matrix matching purposes, iron is included in the analytical program to be prepared. Within the conditions here above, spectral interferences don’t need to be calculated.