Abstract: ⁹⁹Tc^m-sestamibi was the first radiopharmaceutical to be approved by the FDA (Food and Drug Administration) for scintimammography. Some prospective studies have shown that the overall sensitivity of ⁹⁹Tc^m sestamibi scintimammography in detection of breast cancer was 85%, the specificity was 89%, and the positive and negative predictive values were 89% and 84% respectively. Scintimammography plays a special role in various clinical indications such as nondiagnostic or diffcult mammography and evaluation of high-risk patients, tumor response to chemotherapy, and axillary lymph node metastatic involvement.