Environmental contaminants threaten the biological integrity of aquatic and semi-aquatic communities both inside and outside of U.S. National Wildlife Refuges (Refuges). The U.S. Fish and Wildlife Service (FWS) and the U.S. National Biological Survey are developing a new biomonitoring program, the Biomonitoring of Environmental Status and Trends (BEST) Program. The BEST Program is being designed to respond to the effects of contemporary environmental contaminant problems associated with fish and wildlife and their habitats. When fully operational, BEST will evaluate the effects of contaminants on fish and wildlife resources; identify and prioritize national, regional, and local contaminant issues for decision makers; monitor national trends of the presence and effects of contaminants; and provide baseline information to support various contaminant investigation activities. The BEST Program will use an integrated network to evaluate contaminant impacts at the tissue, organism, population, community, and ecosystem levels. The sampling approach will be designed around two major components, trust resources on FWS lands (primarily Refuges) and trust species and their habitats outside of FWS lands. The BEST Program is adopting bioassessment techniques from four broad categories including ecological surveys, biomarkers, bioassays and toxicity tests, and residue analysis. Pilot and demonstration projects will be conducted through fiscal year 1997.