We present a case of breast carcinoma, which was followed by acute leukemia within 1 month of diagnosis of the former. She had undergone a modified radical mastectomy for her breast cancer and had not received chemotherapy or radiotherapy. Acute leukemia as a result of chemotherapy for breast carcinoma is well known. However, patients developing synchronous breast carcinoma and acute leukemia, in the absence of any chemotherapy or radiotherapy, are rare.