Four applications of artificial tracers in the study of sanitary landfill sites are identified; confirmation of leachate contamination, determination of on-site hydrology, determination of hydraulic properties of landfill materials and prediction of leachate contamination and dilution. These applications are illustrated by seven tracing experiments undertaken at a landfill site in the Jurassic Great Oolite Limestone of the Cotswolds using fluorescent dye tracers. The tracers proved non-conservative, which limited their use in determination of hydraulic properties, but were still detectable over 5 months after injection. Background fluorescence due to organic materials in landfill leachate and chemical instability caused problems in analysis, but these could be overcome. Overall the tests were successful in identifying the sources and paths of leachate leakage in the landfill, permitting design of effective remedial measures, and in demonstrating the risks of leachate contamination at surface streams and springs in the vicinity.