Stephen R. Hutchins, Ph.D., Research Environmental Scientist; USEPA National Risk Management Research Laboratory, Ground Water & Ecosystems Restoration Division, Robert S. Kerr Environmental Resarch Center; 919 Kerr Research Drive, Ada, OK. An overview of several projects will be presented on a research program currently underway at ORD’s Ground Water and Ecosystems Restoration Division (GWERD) to evaluate CAFO impacts on ground water quality. The overall research objectives are to characterize the potential for ground water impact from a variety of stressors associated with different types of CAFOs, to develop tools to determine sources and specific mechanisms of impact, and to then collectively use these data to develop effective risk management strategies for protection of ground and surface water quality. Initial specific research objectives were to evaluate selected swine CAFO operations to understand which stressors pose the greatest risk for transport into ground water under site operating conditions. Much of the work initially focused on the field site at Canton, Oklahoma, which demonstrated that land application of liquid swine waste led to ground water contamination by nitrate. Stable nitrogen isotope data were found to be useful in helping to identify the source. Other stressors, such as estrogen hormones (which are endocrine-disrupting chemicals) and antibiotics, were not detected in ground water at that site. However, estrogens, as well as nitrate and ammonia, were found in ground water at another site which had been directly impacted by a leaking lagoon. Based on these studies, secondary research objectives have been identified and research is in progress to 1) expand the current efforts to include other types of CAFOs, 2) further develop analytical tools for detection of estrogen conjugates, 3) expand the use of stable isotope tools for source tracking of nitrate, and 4) evaluate the effectiveness of Nutrient Management Plans (NMPs). A survey of swine, poultry, dairy, and beef feedlot lagoons has recently been completed and will be discussed, with emphasis on estrogens and estrogen conjugates. Other ongoing projects that will be briefly described will include the Regional Applied Research Effort (RARE) projects that have been established through EPA Regions 4 and 6 with USDA and USGS to conduct research on stable isotopes and NMP effectiveness, and an Interagency Agreement (IAG) with USDA to conduct an extensive study on NMP effectiveness.