The National Oceanic and Atmospheric Administration (NOAA) created the National Status and Trends (NS&T) Program in 1984 to address national concerns over the quality of the coastal marine environment. One of its goals is to assess spatial distributions and temporal trends in chemical contamination. To meet that goal, the NS&T Mussel Watch Project was formed in 1986 to measure concentrations of a broad suite of trace metals and organic chemicals in surface sediments and whole soft-parts of mussels and oysters collected from about 300 coastal and estuarine sites. Here we summarize results from eight years of annually collecting and analyzing mollusks. The most important of these results indicates that contamination is decreasing for chemicals whose use has been banned, such as chlorinated hydrocarbons, or severely curtailed, such as cadmium. For other chemicals there is no evidence, on a national scale, for either an increasing or decreasing trend. There are some sites where trace element concentrations are both "high" and increasing.