We report 2 adults with a past history of radiation therapy to the head for malignancy (one with primary B-cell lymphoma confined to the skull and the other with multiple hemangioendotheliomas) who developed episodes consistent with migraine with and without aura. In addition to more typical migraine attacks and beginning many years after their radiation therapy, both patients have experienced infrequent, stereotyped, prolonged, reversible neurologic deficits associated with headache, occasional seizures, and striking, transient, cortical gadolinium enhancement of the posterior cerebral gyri on MRI. Interictal MRI brain scans show stable abnormalities consistent with the patients' previous radiation therapy. The neurologic deficits often progressed over a few days, sometimes lasted weeks, and completely resolved. Electroencephalograms did not show epileptiform activity. Thorough investigation showed no residual or recurrent tumor and no recognized cause for the patients' attacks. We postulate a causal relationship between the patients' remote radiation therapy and their prolonged, strokelike migraine attacks. Radiation-induced vascular changes could provoke the episodes, with or without an underlying migraine diathesis. Recognition of this syndrome can help avoid invasive testing.