Dual-energy subtraction mammography was performed for breast examinations. To obtain a dual-energy subtraction image with a digital radiography unit, high- and low-energy images were obtained at an appropriate time interval under different x-ray exposure conditions. In about 50% of the patients with breast cancer included in this study, we obtained better diagnostic accuracy with dual-energy subtraction images than with conventional mammography. In some cases of breast cancer, it is possible to diagnose intraductal spread of this lesion on the subtracted images. Furthermore, abnormal lesions commonly observed on mammography in cases of fibrocystic disease tended to be erased on subtracted images. Thus, dual-energy subtraction mammography provided useful information for diagnosing breast diseases. However, there were several cases in which the subtracted images lacked sufficient image quality, and several technical problems with subtraction are thought to remain.