Objective: To report a case of an ectopic pituitary adenoma in the clivus. Methods: The clinical, laboratory, and imaging findings of the case are reviewed, and the embryogenesis of the pituitary gland, the pathophysiologic features of this condition, the diagnosis, and the treatment options are discussed. Results: A 20-year-old man presented to a local physician because of a milky nipple discharge of 2 months' duration. He was otherwise healthy. Findings on physical examination were unremarkable except for the milky discharge from both nipples on expression. Serum prolactin, insulinlike growth factor-I, and a-fetoprotein were measured. Magnetic resonance imaging of the brain revealed a 13-mm erosive mass in the clivus. Surgical excision of the lesion was undertaken because of the propensity for aggressive lesions in this anatomic location and the high likelihood of complete resection. After the resected tissue was examined, the patient was diagnosed as having an ectopic prolactin-producing pituitary adenoma. His endocrinologic function normalized after resection, and no further therapy was needed. Conclusion: Ectopic prolactinoma in the clivus is an uncommon lesion. Surgical resection was undertaken in our patient because of the uncertainty of the diagnosis and the aggressive natural history of more common tumors of the clivus, such as chordomas. Resection provided a cure in this patient. Although it is possible that a successful trial of dopaminergic therapy would have obviated surgical intervention, this approach would be associated with additiona risks if the diagnosis were incorrect. (Endocr Pract. 2009;15:143-148). © 2009 AACE.