This document is the product of an ongoing effort begun at a 4-day workshop sponsored by the Rocky Mountain Region of the USDA Forest Service, held in December 1990 in Estes Park, Colorado. Workshop participants gathered in groups to work on pollution impacts in three specific areas: aquatic ecosystems; terrestrial ecosystems; and visibility. Because the groups met separately and subsequently worked independently, the reports they generated differ considerably in format and style. They all focus, however, on providing the Forest Service with information that may be used to identify and develop sensitive receptors and limits of acceptable change for assessing air pollution impacts on air quality-related values in wildernesses within the Rocky Mountain Region of the Forest Service. The reports also address needs and recommendations relating to modeling or predictive techniques, monitoring, and research.