In 13 cases, a breast abnormality was inadvertently removed during stereotactic core biopsy, and a 0.5- or 1.0-cm-long endovascular embolization microcoil was placed to mark the biopsy site. In seven patients, the microcoils allowed successful preoperative localization of the lesion site. In six patients, 6-month follow-up mammograms showed no change in microcoil position. Placement of embolization microcoils helped localize the site of breast lesions removed during stereotactic core biopsy.