DCIS is an early localized stage of mammary malignancy that has an especially favorable prognosis with appropriate management. It seems to be a direct precursor to invasive carcinoma of the breast and has the same therapeutic options. There are still many outstanding issues to be resolved before the intriguing potential of this disease can be fully realized. Any physician involved in the management of diseases of the breast must be committed to a thorough understanding of all aspects of the biologic factors of this entity, so as to be able to rationally provide appropriate advice and treatment. Ongoing investigations should advance the knowledge and experience with this disease in future years.