In April 2000 researchers from around the world met in Lexington, Kentucky to bring together the very latest information on the chemistry and biological effects of the environmental pollutants known as Polychlorinated Biphenyls (PCBs). The result is a comprehensive and extensive treatment of the very latest findings on all significant subjects relating to PCBs and their health risks. The thorough introduction and sixty-two scientific papers presented here represent the most up-to-date research by scientists in government, private industry, and academia.