Meteorological evidence demonstrated that pollutants discharged into the atmosphere in the District of Columbia, Virginia and Maryland are transported across their respective borders into neighboring jurisdictions subject only to the vagaries of wind and weather. It was further shown that in the National Capital metropolitan area topography allows free air movement across political boundaries because of the absence of significant natural or artificial obstructions. That such discharges cause or contribute to interstate air pollution which endangers health or welfare was demonstrated by a number of experts in many fields. Recommendations for abatement are summarized.