The increased use of screening mammography in the past two decades has led to a marked increase in the number of patients diagnosed with ductal carcinoma in situ. Treatment has traditionally involved mastectomy, but this approach has come under increasing scrutiny, and the treatment of ductal carcinoma in situ has become one the most controversial areas in the field of breast disease. This article reviews current concepts regarding the diagnosis, natural history, and treatment of ductal carcinoma in situ.