The Albemarle-Pamlico Study Unit is one of 20 National Water-Quality Assessment (NAWQA) studies begun in 1991 by the U.S. Geological Survey (USGS) to assess the Nation's water quality. One of the missions of the USGS is to assess the quantity and quality of the Nation's water resources. The NAWQA program was established to help accomplish this mission. The Albemarle-Pamlico Study Unit, located in Virginia and North Carolina, drains an area of about 28,000 square miles. Four major rivers, the Chowan, the Roanoke, the Tar-Pamlico and the Neuse, all drain into the Albemarle-Pamlico Sound in North Carolina. Four physiographic regions (areas of homogeneous climatic, geologic, and biological characteristics), the Valley and Ridge, Blue Ridge, Piedmont and Coastal Plain Physiographic Provinces are included within the Albemarle-Pamlico Study Unit. Until 1991, there was no single program that could answer the question, 'Are the Nation's ground and surface waters getting better, worse, or are they staying the same?' A program was needed to evaluate water quality by using standard techniques to allow assessment of water quality at local, regional, and national scales. The NAWQA Program was implemented to answer questions about the Nation's water quality using consistent and comparable methods. A total of 60 basins, or study units, will be in place by 1997 to assess the Nation's water quality.