PURPOSE: The purpose of the study is to determine the mammographic and ultrasonographic features of the breasts with partial mastectomy and irradiation. MATERIALS AND METHODS: The authors reviewed the serial studies of 23 patients who had partial mastectomy and irradiation. Mammogram and ultrasonogram were perfomed every 6 months after surgery in all patients. Sixteen of 23 patients took mammogram and ultrasonogram 1 month after surgery additionally. We evaluated skin thickening, edema, new calclfication, and postoperative scar. RESULTS: Skin thickening was observed in all patients at initial study after surgery and were most pronounced 6 months after surgery. In the most of patients, increased breast density suggesting edema was seen at the initial study after surgery. Skin thickening and edema were most pronounced 6 months who had retumed to normal state 18 months after surgery in 3 of 5 patients who had serial studies until 18 months after surgery. Scars were noted in 20 of 23 patients and 9 of 20 patients had scars 6 months after surgery. The postoperative changes including skin thickening, edema, and scar were most pronounced at 6 months after surgery and had retumed to normal at 18 months after surgery. CONCLUSION: We conclude that postoperative imaging should be obtained 6 months after surgery, followed by every 6 month intervals, which can be effective in differentiating postoperative scar from recurrent carcinoma and can avoid invasive studies.