VARIOUS surgical procedures have been touted for moyamoya disease, each intended to increase cerebral blood flow distal to the occluded carotid arteries.1-3 The studies promoting these procedures are typically enthusiastic but uncontrolled. Most patients who undergo surgery do well, and blood flow through the newly placed vessels can often be demonstrated,2 but the natural history of moyamoya has never been well defined because even mildly affected patients usually undergo surgery.4 Reports that demonstrate enhanced cerebral blood flow to the cerebral cortex following a revascularization procedure are more convincing, but generally lacking is any attempt to control for other factors and objective evidence that the patient's clinical outcome has been improved by the procedure. As Vladimir Hachinski5 noted, "Without pioneering there will be no progress and without a clinical trial there will be no proof."