The advantages of using elemental information to assist in the interpretation of x-ray diffraction (XRD) data are well known and many of the modern search/match algorithms utilize chemical information to make the procedure faster and more reliable (1). Elemental data can also be used to facilitate the quantitation of phases ideittified by x-ray diffraction, in some cases eliminating the need for performing the quantitation based upon the diffraction pattern. There are certain advantages to this approach. The first is that certain difficulties encountered in XRD quantitation such as line overlap, particle statistics, preferred orientation, microabsorption, extinction, and lack of pure Standards are alleviated. The second is that the elemental analysis is, as a rule, easier and more sensitive than the diffraction technique. It therefore should be possible to increase the ease and the accuracy of quantitative phase analysis by utilizing the chemical data available. Since most materials submitted for XRD analysis are in form acceptable for x-ray fluorescence (XRF) analysis, this is the quantitative elemental technique of choice. However, it should be noted that other elemental analysis techniques can be used instead of XRF to furnish the chemical analysis.