Many surface waters in the Adirondack region of New York State have low alkalinities due to a carbonate-poor geology. This condition makes these waters particularly sensitive to the high acid ion deposition associated with the region's air-shed. Since 1975, pH and alkalinity measurements have been made on 849 ponded waters to determine the scope of water quality impacts associated with acid ion deposition and to provide a baseline inventory for indexing future assessments. The present condition of surface waters is described on the basis of summertime, one meter depth, pH measurements obtained with a pH meter under air-C0₂-equilibrium conditions. Twenty-five percent of the waters in the survey registered pH readings below 5.0. These waters comprise 10,460 surface acres. Comparisons of historic and post-1974 acidities are made. Relationships between meter pH, colorimetric pH, alkalinity, conductivity, calcium, lake surface area, lake surface elevation and geographical location are discussed. Changes in fish species composition and sport-fishing yields observed in waters exhibiting increased acidity are reviewed.