FREDERICK C. KOPFLER is presently Chief of the Chemical and Statistical Support Branch, Toxicology and Microbiology Division, Health Effects Research Laboratory, U.S. Environmental Protection Agency, Cincinnati, Ohio. He obtained his BS in chemistry from Southeastern Louisiana University in 1960 and advanced degrees in biochemistry and food science from Louisiana State University. After completing a National Research Council-sponsored postdoctoral appointment in the Pioneering Research Laboratory for Animal Proteins at the U.S. Department of Agriculture, he was involved in environmental research with the U.S. Public Health Service and, since its formation in 1970, has been associated with the U.S. Environmental Protection Agency (EPA). Dr. Kopfler has worked closely with epidemiologists in designing studies of the relationship between drinking water chlorination practices and cancer incidence in consumers, and studies of mineral and trace element content of drinking water and the occurrence of cardiovascular disease. His current research areas include isolation of organic contaminants from water for toxicological testing and the identification of the reaction products of chlorine with biological chemicals., GUNTHER F. CRAUN has served in various capacities over the past twenty years as an environmental engineer and epidemiologist with the U.S. Public Health Service and the U.S. Environmental Protection Agency (EPA). Since 1970, he has been associated with EPA's drinking water and health research activities. His current research interests include relationships between drinking water contaminants and cardiovascular disease, cancer, and infectious diseases. He received his education in civil engineering (BS) and sanitary engineering (MS) at Virginia Polytechnic Institute, and public health (MPH) and epidemiology (MS) at Harvard University. He is registered as a professional engineer in the Commonwealth of Virginia., Mr. Craun has authored and coauthored numerous articles in the international scientific, public health, and engineering literature. The American Water Works Association and the New England Water Works Association have recognized Mr. Craun for his work on waterborne disease outbreaks and trace metals in the drinking water of the Boston metropolitan area. The EPA awarded Mr. Craun a meritorious performance citation for his participation in the Community Water Supply Study, which identified deficiencies in the nation's public water supplies., Mr. Craun is a member of the International Association of Milk, Food, and Environmental Sanitarians Committee on Communicable Diseases Affecting Man, and from 1977 to 1982 he served as chairman of the American Water Works Association Committee on the Status of Waterborne Disease Outbreaks in the United States and Canada. Mr. Craun served as liaison representative to the National Research Council's Safe Drinking Water Committee from 1974 to 1977, and as a member of the World Health Organization Working Group on Sodium Chloride, and Conductivity in Drinking Water in 1978. He has also served as a member of the Water Pollution Control Federation Research Committee and the International Association on Water Pollution Research Study Group on Virology., Mr. Craun is currently Coordinator of the Environmental Epidemiology Program in EPA's Health Effects Research Laboratory, Cincinnati, Ohio. In his present capacity, he works with a number of other government agencies, including the National Cancer Institute and Oak Ridge National Laboratory, on epidemiological studies of drinking water contaminants. He is also involved in projects with the National Academy of Sciences and the University of Pittsburgh Center for Environmental Epidemiology to identify new research areas and methodologies for environmental epidemiology.