Breast carcinoma and hyperplasia are thought to start in the lining of the breast duct. Mammary ductoscopy is an emerging technique allowing direct visual access of the ductal system of the breast through the nipple. This article reviews and discusses the utility of mammary ductoscopy. Abnormalities can be identified successfully by mammary ductoscopy, and intraductal biopsy can be used when the tumor is a polypoid type. Ductal lavage using microcatheters is effective in identifying malignant cells in high-risk women and this has stimulated interest in exploring the role of mammary ductoscopy in breast cancer screening. Mammary ductoscopy combined with ductal lavage may have a role in the management of patients with nipple discharge, the guiding of breast-conserving surgery for cancer, and in screening for high-risk women. The addition of molecular and genetic analysis of cells obtained by mammary ductoscopy are likely to enhance the use of this technique. Mammary ductoscopy techniques are safe and appear useful for detecting abnormalities in the breast. The additional molecular biologic study or ductal lavage may enhance the ability to direct and limit subsequent surgery when removing the offending lesions.