The decline of many amphibian populations in protected areas across the globe has been a topic of major conservation concern over the past 15 years and has stimulated a tremendous amount of research to identify specific causes. Increasing levels of ultraviolet-B radiation (UV-B, 290-320 nm) as a result of anthropogenic ozone depletion was a leading hypothesis for declines in western North America, and may affect individuals, populations, or species at local to regional scales. From a conservation standpoint, the determination of whether UV-B is or is not important is less informative than understanding the conditions under which particular species’ or life history stages will be strongly regulated by UV-B. Our work built on considerable prior research that focused primarily on evaluating differences in species’ physiological sensitivity to UV-B using laboratory assays and field experiments at a limited number of sites, but lacks a broader ecological context and a rigorous quantitative evaluation of risk. Our work in this area focused on the key role that dissolved organic matter (DOM) in the water at individual sites plays in determining UV-B exposure for a range of amphibian species. DOM is primarily derived from terrestrial plant compounds, which vary as a function of watershed features, and DOM rapidly attenuates short-wavelength radiation, dramatically affecting the UV-B environment within the water column. In collaboration with researchers at the USGS (M. Adams, B. Bury, C. Pearl) and the University of Washington (D. Schindler), we have conducted surveys of amphibian breeding sites across montane areas of the Pacific Northwest, a series of experiments to test the consequences of different UV-B exposures, and regular population monitoring to estimate the demographic rates governing changes in different species dynamics though both time and space.