Atmospheric deposition of acid and other materials may pose a significant threat to some soils and the ecosystems they support. The project objective was to develop maps of the eastern United States that delineate soil areas according to their expected sensitivity to the effects of acid precipitation. Four parameters are important in estimating soil sensitivity to acid precipitation: (1) the total buffering capacity or cation exchange capacity; (2) the base saturation; (3) the management system imposed on the soil; and (4) the presence or absence of carbonates in the soil profile. Cation-exchange capacity was chosen as the primary criterion for classifying the soil regions into non-sensitive, slightly sensitive, and sensitive areas. The North Central States were found to contain, generally, non-sensitive to slightly sensitive soils. The Northeastern States include large regions of slightly sensitive to sensitive soils, and the Central States feature large portions in the slightly sensitive category with varying degrees of inclusions. Maps of these distributions have been prepared for individual states and for the entire eastern United States.