Since 1991, The Bioeffects Program has undertaken a series of regional environmental assessments designed to describe the magnitude and extent of toxic contaminant impacts in our nation's estuarine and coastal areas. Through field studies, we examine the distribution and concentration of over 150 chemical contaminants in sediments, measure sediment toxicity, and assess the condition of bottom-dwelling biological communities. We then integrate this information to develop a comprehensive assessment of the health of the marine habitat. Bioeffects projects are designed to assess the spatial distribution and effects of chemical contamination, and develop indicators of environmental contaminant exposure in water bodies, ranging from small estuaries to large bays and coastal areas. Data are applicable to environmental risk assessments, spill response, damage assessments, and planning future resource management and restoration activities. Using consistent methods over the life of the program allows for comparison of the magnitude and extent of contaminant effects relative to other locations throughout the U.S., and over time. All data are generated following strict performance-based quality control and quality assurance protocols. Data are available to regional, federal, state and local resource managers and the public via publications, presentations, and a website data portal. Bioeffects studies are conducted as a one-time, intensive sampling effort. We sample all sites within the study area synoptically for chemical analyses, toxicity bioassays, and sea floor community assessment. The data reflect a snapshot of the condition of the entire system at a point in time. In brief, field procedures include sampling sediment and the overlying water column. We take two sediment samples at each site, with only the upper 2–3 centimeters of the sediment retained to ensure collection of recently deposited materials. The sediment samples are subdivided for distribution to various testing laboratories. Sediments are analyzed for a large suite of chemical contaminants including metals, chlorinated pesticides (e.g., DDT; PCBs (polychlorinated biphenyls); and PAHs (polynuclear aromatic hydrocarbons)—oil, fuel, and soot; and butyl tins. Additionally, we assess sewage marker pathogens. In some locations, we collect resident fish and invertebrates for body burden analyses and animal health assessments. Toxicity bioassays are conducted to examine sediment toxicity at various levels of biological organization, from biochemical markers to outright mortality. We take a third sample for sea floor community analysis to assess the parameters that mediate population distributions and contaminant impacts. We also develop a water quality profile for the water column that includes standard variables such as temperature, depth, salinity, dissolved oxygen, etc. Detailed descriptions of the sampling techniques and procedures are available by contacting the project manager.