Industrialization has resulted in the emission of a wide variety of organic chemicals into the biosphere. Despite the original source of the organic contaminant, these chemicals have managed to enter drinking water supplies and bioaccumulate in food chains. Of particular interest are the organic contaminants which have been identified in fish and wildlife in the Great Lakes Basin. As this waterway system functions as an important source of drinking water for North Americans, concern has been raised with respect to toxicity and bioaccumulation of these chemicals. Although a vast number of environmental pollutants have thus far been identified, this chapter will focus on just ten chemicals, principally chlorinated benzenes, octachlorostyrene and hexachlorobutadiene. The adult, fetal and neonatal toxicities of these compounds are discussed with emphasis on metabolic and pharmacokinetic factors which influence them.