Elemental analysis by means of X-ray fluorescence (XRF) spectrometry is based on the element-specific electromagnetic radiation induced as a consequence of inner-shell ionization. XRF spectrometry is ideal for the direct analysis of solid samples, but can also investigate fluid samples. On one side, these methods allow the rapid qualitative screening of unknown samples, without any particular sample preparation. On the other hand, it is possible to perform the fully automated quantitative analysis of large sample sets. Further figures of merit are the ’standard-less’ analysis of samples in a non-destructive mode, and detection down to 0.01 %. The availability of portable XRF systems 6 is a further advantage for on-site measurements. The fundamentals are discussed to orient the user, and a survey of instrumental capabilities is provided.