Results are presented of an interlaboratory round-robin study of the application of timeResolved Emission Spectroscopy (TRES) to the speciation of uranium(VI) in aqueous media. This involved 13 independent laboratories, using various instrumental adevices and data 2 analysis methods. In some cases, experimental data from a laboratory were analysed using different softwares. Samples were prepared based on appropriate speciation diagrams and in general were found to be chemically stable for at least six months. Four different types of aqueous uranyl solutions were studied: (i) acidic medium where UO 2 2+ aq is the single emitting species, (ii) uranyl in the presence of fluoride ions, (iii) uranyl in the presence of sulfate ions, and (iv) uranyl in aqueous solutions under various pH conditions, promoting hydrolysed species. Results between the laboratories are compared in terms of number of decay components, luminescence lifetimes and spectral band positions. The potentials and limitations of TRES in uranyl analysis and speciation in aqueous solutions are discussed.