Numerous studies report that ultraviolet (UV) radiation is harmful to living organisms and detrimental to human health. Growing concerns regarding the increased levels of UV-B radiation that reach the earth's surface have led to the development of ground- and space-based measurement programs. Further study is needed on the measurement, modeling, and effects of UV radiation. The chapters of this book describe the research conducted across the globe over the past three decades in the areas of: (1) current and predicted levels of UV radiation and its associated impact on ecosystems and human health, as well as economic and social implications; (2) new developments in UV instrumentation, advances in calibration (ground- and satellite-based), measurement methods, modeling efforts, and their applications; and (3) the effects of global climate change on UV radiation. Dr. Wei Gao is a Senior Research Scientist and the Director of the USDA UV-B Monitoring and Research Program, Natural Resource Ecology Laboratory, Colorado State University. Dr. Gao is a SPIE fellow and serves as the Editor-in-Chief for the Journal of Applied Remote Sensing. Dr. Daniel L. Schmoldt is the National Program Leader for instrumentation and sensors at the National Institute of Food and Agriculture (NIFA) of the U.S. Department of Agriculture. Dr. Schmoldt served as joint Editor-in-Chief of the journal, Computers & Electronics in Agriculture, from 1997 to 2004. Dr. James R. Slusser retired in 2007 from the USDA UV-B Monitoring and Research Program at Colorado State University. He was active in the Society of Photo-Optical Instrumentation Engineers, the American Geophysical Union, and the American Meteorological Society. Dr. Slusser is currently pursuing his interests in solar energy and atmospheric transmission.