Serial cerebral perfusion studies were performed in a patient with moyamoya disease, utilizing N-isopropyl iodoamphetamine (I-123 IMP). The SPECT findings correlated closely with those of a CT scan and magnetic resonance imaging (MRI). In fact, the perfusion defects seen on SPECT studies were larger than those seen on CT and MRI studies. The SPECT findings paralleled the patient's improving clinical course. Cerebral perfusion SPECT studies may be very helpful in the evaluation and follow-up of patients with moyamoya disease.