The U.S. Environmental Protection Agency (EPA) Office of Research and Development (ORD) Regional Science Workshop on Animal Feeding Operations (AFOs) Science and Technical Support Needs was held in College Park, Maryland, December 6-9, 2004. The workshop sessions were structured around the top 10 priority research questions identified by the EPA Regions prior to the workshop. The goals of the workshop were to bring together a broad group of scientists from ORD and other research institutions to explore the available tools for addressing the priority research questions and identifying unmet research and technical support needs required to answer these questions. Question 1: What are the most significant air pollutants, their sources, and their emission rates from AFO operations. What metrics, methods, and models should we use in the future to quantify and monitor these emissions to better understand their relationship to atmospheric deposition and the formation of ground-level ozone and fine particulate matter. Question 2: What are the meteorological and other variables that affect the emissions, transport, and deposition of AFO-related pollutants. Question 3: What methodologies can be used to distinguish the sources of contamination in ground or surface waters (i.e., specific animal species, septic tanks, and fertilizers). Question 4: What specific analytic methods should be used in an environmental setting for the veterinary pharmaceuticals and microorganisms most likely to be found in the environment and linked to adverse human health effects. Question 5: How can we determine the fate, transport, and environmental impacts of pharmaceuticals and pathogens. Are there technologies to mitigate exposures. Question 6: What is the strength of the evidence that demonstrates linkages between exposures to AFO contaminants and incidence of disease, especially infectious diseases caused by pathogenic organisms originating from AFO wastes.