Abstract: Recent advances in endoscopic technology have made visualization of human mammary ducts possible. The purpose of this study was to assess the feasibility and technical factors influencing the ability to successfully visualize the epithelium of the human mammary ductal system. Lacrimal duct probes were used to dilate nipple orifices to 1.2 mm on 42 mastectomy specimens. The Depth of Field Imaging Micro-Minimally Invasive (DOFI® MMI) system consisting of a 1.2 mm rigid ductoscope with a 350 μm working channel was introduced into mammary ducts under air insufflation or saline irrigation. At least one major duct could be dilated and cannulated in all 42 specimens. Visualization of the proximal duct was accomplished in 34 of 42 (81%) specimens, whereas more extensive navigation through the distal subsegmental ducts was achieved in 22 of 42 (52%) specimens. Ductoscopy into the terminal ducts was accomplished in all patients with a previous history of nipple discharge or discharge at the time of the procedure (10 of 10). In three patients with no history of nipple discharge prior to ductoscopy, incidental papillomas were discovered and confirmed by the pathologist. In conclusion, mammary ductoscopy is technically feasible and may have an application as an additional diagnostic modality for patients with pathologic nipple discharge.