Abstract: The western toad species complex, endemic to western North America, includes two montane species that have undergone extensive declines. These are the Yosemite toad, Bufo canorus, in the Sierra Nevada, and the southern Rocky Mountain populations of the boreal toad, B. boreas. In both cases, infection by chytrid fungus appears to have played a significant role. Most declines in the Rockies appear to have occurred before 1980, but a recent episode in Rocky Mountain National Park illustrates the rapidity and severity with which populations of toads can succumb, and that the phenomenon is still occurring. It is unclear whether the fungus infections represent the emergence of a novel pathogen, or instead, external stressors have increased the susceptibility of toads to disease by reducing the effectiveness of their immune systems. Regardless of the cause of past and current declines, climate change in the coming decades may create conditions that will challenge the persistence of these species and others not currently threatened. If predictions of reduced extent and duration of snow cover are accurate, this will create changes in breeding phenology that have already been related to increased mortality in some populations of toads.