Bloody nipple discharge is a complaint that worries both the patient and the physician. Unlike other types of nipple discharge, it signals intrinsic breast disease. A benign etiology is the rule rather than the exception, but this symptom warrants careful evaluation. If there is no palpable mass or mammographic abnormality, bloody discharge from a single duct in a nonpregnant young woman is usually due to a benign intraductal papilloma.