Based on experimental studies with animals we examined 22 patients with pathological (bloody) nipple discharge by cytology, ultrasonography, galactography and the newly developed galactoscopy [Endoscopic-System EndoGnost(R) (Polydiagnost)]. The duct's cannula has an outer/inner diameter of 0.45 mm/0.36 mm and a working length of 30 mm, the endoscope a length of 1200 mm, adapted to a CCD-camera (2500 pixel). All patients underwent surgery and histo-pathological diagnosis. The best diagnostic results were received with galactoscopy (21/22). By using an additional cutter it is possible to obtain a histological sample for diagnosis endoscopically. Galactoscopy is an emerging technique and will expand the spectrum of interventional methods in breast diagnosis.