Due to systematic mammography, DCIS is being seen with increased incidence than in the past. Asymptomatic women screened by mammography show a high incidence of microcalcifications. Lymph node involvement is seen in very few patients. Total mastectomy provides local control and long term survival approaching 100%. Immediate breast reconstruction allows better acceptance of mutilations. Conservative treatment has been advocated for localised DCIS. The classification system dividing DCIS into comedo- and non-comedo subtypes could be an oversimplification because of the frequent histological heterogeneity. Other criteria such as cytological features oncogene activity of C erb 2 and clinical and radiological features must be considered. It has now been demonstrated that DCIS does not have a multicentric distribution. Assessment of lesion size appears to be primordial for breast conservative treatment indications. A relationship has been demonstrated between lesion size and microinvasion. The aim is complete excision with free margins and a cosmetically acceptable postoperative result. Radiotherapy seems to lower the incidence of local recurrences in retrospectives studies. Prospective randomized trials are being conducted to compare lumpectomy with and without radiotherapy.