Between 1990 and 1995 a series of bed sediment, suspended sediment and fresh ¯oodplain samples were collected within the Seine River Basin, in France, to evaluate variations in trace element geochemistry. Average background trace element levels for the basin were determined from the collection and subsequent analyses of bed sediment samples from small rural watersheds and from a prehistoric (5000 BP) site in Paris. Concentrations are relatively low, and similar to those observed for ®ne-grained bed sediments from unaected areas in the United States and Canada. However, the concentrations are somewhat higher than the reference levels presently adopted by French water authorities for areas north of the Seine Basin, which have similar bedrock lithologies. Downstream trace element variations were monitored in 1994 and 1995 using fresh sur®cial ¯oodplain samples that were collected either as dried deposits a few days after peak discharge, or immediately after peak discharge (under 430 cm of water). Chemical comparisons between fresh ¯oodplain deposits, and actual suspended sediments collected during ¯ood events, indicate that, with some caveats, the former can be used as surrogates for the latter. The ¯oodplain sediment chemical data indicate that within the Seine Basin, from the relatively unaected headwaters through heavily aected urban streams, trace element concentrations vary by as much as three orders of magnitude. These trace element changes appear to be the result of both increases in population as well as concomitant increases in industrial activity. This article is a US government work and is in the public domain in the United States.