Mammary ductoscopy (MD) allows visualization of the lactational duct and the morphology of various ductal pathologies can be identified. It provides a new approach for clinical research. The main impact of MD is on the modification of the extent of surgery. MD was used to guide the extent of duct excision in patients with pathological nipple discharge. Multiple duct lesions detected by MD can be excised completely. MD was also used to guide resection in breast-conserving surgery for breast cancer. There was less proximal margin involvement with the use of MD. MD also helps to spare unnecessary surgery. In patients with nipple discharge, duct excision can be avoided in those with a normal ductoscopy. Nipple-sparing mastectomy (NSM) is cosmetically superior to traditional mastectomy but there are concerns about the oncological safety with nipple-areola preservation. MD can be employed to exclude major duct involvement and this may help to select patients for NSM. We are currently studying the role of MD in identifying major duct involvement in potential patients undergoing NSM. MD has technical limits. MD cannot examine the distal duct and biopsy facility is limited. No therapeutic facility is available at present but these technical limits will be resolved when the next generation of MD is available. In conclusion, MD has made a significant impact on breast surgery. The technology is developing and with continued research, the role of MD in breast surgery will continue to expand.