Nipple discharge is a common breast complaint which is usually benign, but can be a sign of malignancy. There are multiple etiologies, including nipple stimulation; medications such as antihypertensives, phenothiazines, opiates, H2 receptor blockers, and estrogen preparations; endocrine and metabolic disorders; pituitary tumor; and benign and malignant breast conditions. Nipple discharge can be divided into the following three categories to help guide evaluation and treatment: (1) physiologic,(2) galactorrhea, and (3) pathologic. Galactorrhea is related to increased prolactin levels and therefore a pituitary tumor should be ruled out. Pathologic discharge is commonly unilateral, localized to a single duct, spontaneous, intermittent, persistent, and ranges from bloody to clear in color. Occult blood and cytology smears, mammography, and biopsy should be initiated to determine the exact cause and guide treatment.