X-ray Fluorescence Spectroscopy (XRF) has reached the stage where it is classified as a mature analytical technique. The theoretical principles are well understood. In addition modern instrumentation demonstrates enhanced generator and temperature stability. High sensitivity is possible even for light elements and effective matrix correction software is available to the modem day spectroscopist. Apart from its continued applications in research and development, XRF has become u routine process control tool. X-ray Powder diffraction (XRD), on the other hand, has with minor exceptions as in the cement industry, largely remained a research tool, despite being an older analytical technique than XRF. XRD has progressed significantly in the past decade from a mainly qualitative technique for the identification of crystalline materials to a quantitative tool with the advance of more powerful software packages. This software has improved instrument control, but also quantification and structure determination using the Rietveld method. Consequently, XRD is rapidly entering the process control environment. In this paper the authors demonstrate, with practical examples from different industrial applications, how combined XRF and XRD use can provide truly quantitative phase analyses. XRF is used to verify XRD data and visa versa. The data obtained in this study clearly illustrate the value that can be added to either technique if XRF and XRD data are used together, and indicate some applications in routine process co.