Therapeutic irradiation produces alterations in normal tissue which, when visible on diagnostic x-ray examinations, may be confused with recurrent tumor or other unrelated conditions. Therapeutic irradiation of breast carcinoma may produce gross effects in the lungs, bone, breast, heart and great vessels, esophagus, liver, and spinal cord. The radiographic appearance of such changes is presented and contrasted with changes secondary to the malignancy itself or benign inflammatory processes. Recognition is imperative for proper management.