Soil properties including moisture, mineralogy and specific surface area are important determinants of the rate of base cation release from forest soils.  In acid-sensitive regions where there are ongoing efforts to quantify mineral weathering rates in support of emission management policies, specific surface area is rarely measured.  Instead, surface area is most often estimated according to existing predictive methods.  Specific surface areas of acid-sensitive mineral soil series located downwind of a major acid precursor emission source were measured and used to evaluate these commonly used predictive equations.  A regionally-specific predictive equation for surface area was also developed using more easily measured soil properties (e.g. soil texture), and the error in resulting weathering rate estimates (generated using a process-oriented soil chemical model) associated with the use of these predictive equations was quantified.  This research highlights the limitations of using these predictive methods and suggests the importance of measuring the specific surface area of these sandy soils which are among the most acid-sensitive in Canada.