FLUO is a computer program that corrects XANES data measured with the fluorescence technique for self-absorption effects. These effects are most significant when the element whose XANES is measured is concentrated and/or when it is a heavy atom surrounded by lighter atoms. The program can be used to correct data taken on liquid solutions as well as on crystalline and amorphous solids. The code can also be used for energy alignment of several data scans and to calculate their energy derivatives.