【Abstract】Objective To evaluate the application of duct endoscopy in the diagnosis of breast diseases characterized by nipple discharge. Methods One hundred and sixtynine consecutive cases from October 2003 to September 2004 who had duct endoscopy for nipple discharge were reviewed and followed up. Results Of 169 cases, 79 ductitis, 62 intraductal papilloma, 9 intraductal carcinoma in situ, 19 without breast diseases were diagnosed under duct endoscopy. During following up, the diagnostic accuracy of intraductal papilloma and intraductal carcinoma in situ with duct endoscopy was 89.8%(44/49) and 55.6%(5/9),respectively. There was only one patient who had breast pain and mild skin redness which was cured with oral antibiotics for 3 days. Conclusion Duct endoscopy is an only technique to explore the etiology for duct discharge under vision. It is direct, safe and effective, with a high accuracy.