Total reflection X-Ray Fluorescence spectroscopy(TXRF)today is a powerful multi-elemental method for trace and ultra-trace analysis of different kind of samples that can be grouped as follows: environmental samples(as water,soil,aerosols,deposits,plants),geological and mineralogical samples(as ore,crystals,mineral raw materials),biological samples(as blood,serum,urine,human tissue),food samples(as fish,fruit,meat,nuts,mushroom)and many others.Presently,two international standards for the contamination analysis on silicon wafers by TXRF exist,but none for the chemical analysis of the beforehand listed sample groups.Recently,a workgroup at the ISO Technical committee 201 started a project “Technical Specification for the use of TXRF in biological and environmental analysis”(WD 18507).The objective for the document is to provide a framework on the uses of Total reflection X-Ray Fluorescence(TXRF)for biological and environmental elemental qualitative and quantitative analysis of elements.It is meant to help technicians,biologist,environmental scientists,and engineers to understand the possible uses of TXRF for elemental analysis by providing the guidelines for the characterization of biological and environmental samples with TXRF spectroscopy.This paper discusses the results of the first inter-laboratory test on TXRF analysis of water samples.A wide range of water samples was considered in this study,including drinking waters,industrial waste waters and desalinated water.Many sources of data dispersion are highlighted: water sample type,sample preparation,spectral fitting and quantification procedures.In addition an outlook about future TXRF projects of the ISO workgroup is shown.