Regulations pertaining to development of groundwater resources of Denver Basin bedrock aquifers are based in part on estimates of specific yield. To examine spatial variation in specific yield, data from the Castle Pines and Kiowa research cores in east-central Colorado were used to develop a west-to-east cross section of the Denver Basin. Specific yield varied within each aquifer according to geology and distance from the sediment source, the Rocky Mountains. Laboratory measurements of specific yield from deep core samples were considerably lower than estimates obtained previously by the State of Colorado from outcrops along the basin margins. Consideration should be given to this disparity in specific yields to ensure that the volume of groundwater stored in the Denver Basin bedrock aquifers is not overestimated.