Wyburn-Mason syndrome (WMS), also known as the Bonnet-Dechaume-Blancsyndrome, is a rare non hereditary phakomatosis characterized by congenital retinal, orbital, and brainstem (usually midbrain) arteriovenous malformations (AVMs), and, less frequently, facial AVMs. With the increased availability of noninvasive brain imaging, intracranial AVMs are detected. Recognition of the association between the retinal and intracranial lesions is important because it allows early identification of the associated intracranial and facial AVMs. This chapter discusses the historical features, pathophysiology, and treatment options for WMS. Retinal AVMs usually do not grow or bleed, and are usually not responsible for significant visual loss. Due to their size and location, WMS AVMs are usually not amenable to surgical removal or radiosurgery. Embolization carries an increased risk because the lesions share a blood supply with vital brainstem structures. Therefore, patients are usually left untreated until the AVMs bleed, at which time heroic measures may be necessary.