The effect of sulfates on cloud microphysical and optical properties have been studied using data from a rural mountaintop location in the Mt. Mitchell State Park, North Carolina. Although the amended Clean Air Act has limited the sulfur emissions beginning 1990, we found the sulfate concentrations greater during 1993--97 compared to that during 1986--89. Cloud albedo inferred from satellite data and calculated from surface observations does not indicate a monotonic increase with increasing sulfates. The direct and indirect (cloud-mediated) sulfate forcing are assessed to be -4.8 and 4 W m-2. These values exceed current model predictions as evaluated by other investigators. Surface temperature records of the region during 1949--94 indicate a cooling trend tacitly supporting our assessment. ¿ 1999 American Geophysical Union