Atmospheric deposition of pollutants, including polychlorinated biphenyls (PCB), has been recognized as a significant contributor in many locations to water quality problems, including toxic contamination of fish and bioaccumulation in wildlife and humans. The U.S. Environmental Protection Agency (U.S. EPA) has been directed by the Clean Air Act to consider the contribution of atmospheric deposition to pollution in the Great Waters, which comprise the Great Lakes, Lake Champlain, Chesapeake Bay, and many of the estuaries of the coastal United States. PCB are included in the group of pollutants of concern for the Great Waters. Background information on the sources, deposition, and environmental concentrations of the pollutants of concern is summarized in detail in a series of reports, the most recent of which is Deposition of Air Pollutants to the Great Waters Third Report to Congress (U.S. EPA 2000), hereafter referred to as the Third Report to Congress. U.S. EPA is no longer required to submit reports to Congress on deposition of air pollutants to the Great Waters. However, much new information related to environmental concentrations, deposition trends and sources of PCB in the Great Waters has been published since the Third Report to Congress, and is compiled here. The recent research also is compared to findings described in the Third Report to Congress. References are provided at the end of this summary. The recent scientific research highlights the declining trend in PCB concentrations and the associated ecosystem health improvement in the Great Waters. At the same time, the research also points to continuing concerns due to PCB contamination.