Ellis B. Cowling was educated at the State University of New York College of Forestry at Syracuse University. He completed Ph.D. degrees in plant pathology and biochemistry at the University of Wisconsin and in physiological botany at the University of Uppsala in Sweden. He is presently Assistant Director, North Carolina Agricultural Research Service, Associate Dean for Research, School of Forest Resources at North Carolina University. Dr. Cowling is also Chairman of the National Atmospheric Deposition Program. In 1981 he was appointed United States Co-chairman of a CanadianUnited States joint Scientific Committee on Acid Precipitation. This committee was established by the National Academy of Sciences and the Royal Society of Canada. Dr. Cowling is President of The Acid Rain Foundation, Inc., a public, tax-exempt organization aimed toward public awareness, education, and research. [Editor's note: Some portions of this article have been published previously.] In recent decades, acid rain has become a dominant feature of people-induced change in the chemical climate of the Earth. Wherever fossil fuels are burned, metal ores are smelted, and materials are processed on a large scale, various gaseous, aerosol, and particulate waste products are released into the atmosphere. These substances and their reaction products are dispersed by meteorological processes and deposited on vegetation, soils, and surface waters, often at great distances from the source of emissions. Concern has arisen in many countries about effects on forests, fish, crops, water quality, materials, and human health. The result is a growing concern among scientists and the public about international exchange of air pollutants, wet and dry deposition of strong acids and other acidifying substances, as well as the associated deposition and mobilization of toxic metals and the leaching of nutrient substances.