U.S. Geological Survey U.S. Geological Survey Samples of stream-bottom sediment were collected at 37 sites in the Willamette and Sandy River basins, Oregon, during August and September 1992 as part of three ongoing studies. The sites represent reference (forested) basins and basins exposed to anthropogenic inputs. The latter include municipal and industrial point sources, and nonpoint-source contributions from various land-use activities, such as urbanization, agriculture, and mining. A primary objective of the sampling design was to determine the occurrence and distribution of trace elements associated with stream-bottom sediment. Twelve of the 37 stream sites were sampled as part of the Willamette National Water-Quality Assessment (NAWQA) and represent a density of about one site per 2,600 square kilometers. Preliminary results for trace-element concentrations in bottom sediment from these sites indicate that (1) lead concentrations were elevated at most sites relative to reference sites, (2) maximum zinc concentrations were found in urban basins, (3) the highest copper concentration occurred downstream from historic complex sulfide-ore mining activities, (4) increased manganese concentrations were found in urban and agricultural basins compared to reference basins, and (5) iron concentrations were unrelated to land use. Elevated arsenic concentrations appear to be associated with a natural geologic source. Results from the two remaining studies will increase the average sample density to one site per 800 square kilometers in the combined Willamette-Sandy basin and will provide a density of one site per 170 square kilometers in the Tualatin subbasin of the Willamette River basin. These data will provide an opportunity to evaluate the effect of increased sample density on our ability to determine associations between land use and stream-bottom trace-element concentrations.