In the eastern U.S., there are considerable areas above 800 m where cloud/fog deposition is an important component of the deposition to ecosystems.  Many of these areas include National Parks, protected Class I and Wilderness areas, and other preserves with rare and endangered species and ecologically important habitats.  Protections of ecosystems in Class I and Wilderness areas from air pollution are mandated by Federal laws such as The Clean Air Act (CAA) and Wilderness Act.  In addition, many of these landscapes are also sensitive to terrestrial and aquatic acidification because of their geology and landscape position. Over the past two decades, interest in better understanding of atmospheric inputs of pollutants to terrestrial and aquatic ecosystems has increased substantially within the scientific community through the use of the critical load (CL) approach. In order to develop scientifically defensible CLs and to evaluate whether ecosystems are protected from deposition resulting from air pollution, it is essential to have estimates of all components of deposition.  This is particularly important for areas at high elevation where cloud/fog deposition is high and where many wilderness and sensitive ecosystems occur.  Critical loads are being used more and more to assess management and regulations decisions.  Critical loads help to inform whether a forest, stream, or area is at risk of being ecologically harmed from deposition caused by air pollution.  In this case study, we examine the importance of cloud/fog deposition on CL exceedances (i.e., deposition > critical load) in areas above 1000 m in the Great Smoky Mountains National Park (GSMNP) in the southeastern United States, with parts in Tennessee and North Carolina.