From the USGS National Analysis of Trace Elements, this new page offers a recent, much publicized map "that shows where and to what extent arsenic occurs in ground water across the country," a new fact sheet ("Arsenic in ground-water resources of the United States"), and a detailed report ("A retrospective analysis on the occurrence of arsenic in ground-water resources of the US and limitations in drinking-water-supply characterizations"). The site also contains data of arsenic concentrations for 18,850 ground-water samples collected between 1973 and 1997. In addition, users will find links to other sites with information on arsenic in ground water.