The design and objectives of the program for evaluating stream quality in North Carolina are described. Using water-quality and streamflow data collected since the 1940's, a study is underway to define certain variations in water quality, to quantify the effects of man 's activities on water quality, and to determine long-term trends at key locations on the State 's major river. Data collected from 47 unpolluted stream sites were used to estimate average concentrations for naturally occurring constituents during periods of high and low flow. Methods are described for estimating constituent loads derived from both natural sources and sources of pollution. (Woodard-USGS)