In many patients with superficial siderosis of the central nervous system (CNS) no source of bleeding can be established, despite extensive examinations. The authors report a patient with superficial siderosis and a spinal arteriovenous malformation (AVM) that was not visible on magnetic resonance (MR) imaging or myelography but was identified on angiographic studies. This 71-year-old man presented with a 2-year history of progressive gait difficulties and hearing loss. Examination showed ataxia, hearing loss, and quadriparesis. On MR imaging superficial siderosis of the brain and spinal cord as seen; however, MR imaging of the CNS, as well as cerebral angiography and myelography studies, did not reveal the source of hemorrhage. Spinal angiography revealed a small slow-flow pial AVM at the C-5 level originating from the anterior spinal artery. A C-5 corpectomy was performed and the AVM was obliterated. The patient did well and reported no further progression of his symptoms during 3 months of follow up. Spinal angiography is indicated to complete the evaluation of patients with superficial siderosis, even if results of spinal MR imaging and myelography studies are normal. Obliteration of spinal AVMs may successfully prevent the progression of superficial siderosis.