Results of an investigation of water quality and pollution in the North Branch of the Potomac River and its tributaries are presented. This survey was requested by the Corps of Engineers to aid in developing a comprehensive water resources plan for the Potomac River Basin. The scope of the study includes: reconnaissance of sources of municipal and industrial pollution and their effects on the stream; determination of water quality objectives for the stream affected by wastes; assembly of stream flow records and analysis of low-flow conditions; investigation of water quality, particularly in relation to acid mine drainage and suitability after storage as a source of water supply; estimates of desirable minimum stream flows in combination with reasonable treatment and control measures for existing and contemplated future population and industrial development conditions.