As part of a wider effort to characterise the origin and pattern of distribution of trace elements in urban environments, a sampling campaign of soils, sewage sludge from municipal waste water treatment plants, and composted sludge, was carried out between 1994 and 1996. All the samples were oven dried, acid digested and analysed by ¡CP-AES. The information thus gathered strongly suggests that the two main sources of trace elements in urban soils are the deposition of atmospheric particles generated from traffic (and, to a lesser extent, from other urban sources), and the application of composted sewage sludge. Agproved to be an excellent tracer of the latter process, since sewage sludge is the only significant urban source of this element. Furthermore, the difference in Ag concentration between soils with and without compost application is from 5 \ig/g for the former to below 1 /lg/g for the latter