This article examines recent developments in the interpretation of the words “addition,” “pollutant,” and “point source,” as used in the Clean Water Act. These words have been the subject of much controversy and many interpretations as the CWA leaves them undefined. The Supreme Court has concluded most notably that the transfer of polluted water within the same body of water does not constitute “addition,” however the transfer of pollutants from one body of water into another is addition. Similarly, much controversy has surrounded the possibility of pesticides, lead shot and erosion as additions. Most recently courts have found that pesticides added to a river to eliminate pestilent fish species is not an addition. With regard to lead by-products and dredged sand debris, courts have gone the other way and found that both materials are additions. Finally, with regard to point sources, conveyances such as gullies and ditches have been found to be point sources, but mining cases present more difficulty. The court has held that the “mere presence” of identified chemicals in water does not constitute a violation of the CWA because such chemicals occurs naturally.