This Technical Report describes the results of the inter-laboratory testing of the chemical analysis of cement by x-ray fluorescence. In the first instance, the inter-laboratory testing was carried out in Japan and in Asian countries in accordance with JIS R 5204:2002. A total of 30 laboratories, 16 in Japan and 14 outside Japan, participated in the original testing programme. A further 12 European laboratories participated in tests with the same materials in 2005 in accordance with EN 196-2, a development by CEN/TC 51/WG 15/TG 1 of JIS R 5204. The latest version, developed as ISO 29581-2, is, as of the date of publication of this Technical Report, in the process of being circulated for technical enquiry. The test samples used were Portland cement conforming to CEM I of EN 197-1 and a mixture of Portland cement and blast furnace slag. The mixture corresponded to the composition of Portland blast furnace slag cement, class B, specified in JIS R 5211 and CEM III/A of EN 197-1. Cement reference materials for x-ray fluorescence analysis (No. 601A) are used for the calibration standards, and certified reference materials JCA-CRM-1 and JCA-CRM-2 are used as the validation materials. Constituents analysed include SiO2, Al2O3, Fe2O3, CaO, MgO, SO3, Na2O, K2O, TiO2, P2O5, MnO and SrO. The loss on ignition is also determined. The ISO round robin is a method-performance study conducted under close to optimum conditions with clear calibration and measurement guidelines. This is conducive to producing “best practice” values representative of the ideal situation. However, ISO 29581-2 is intended for use under everyday conditions in laboratories that operate to “good practice”. Annex D sets out the results of some international round robins carried out by a large number of laboratories demonstrating the suitability of ISO 29581-2 as a means for comparing the everyday performance of laboratories.