Migraine and the MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) syndrome have some clinical features in common. First, cerebral infarctions, most often in the posterior cerebral regions, which are a main symptom of MELAS, may complicate migraine. Second, migrainous headache with vomiting is also a characteristic feature of the MELAS syndrome. Less frequently, hemicranial headache is present in another mitochondrial disease, myoclonic epilepsy with ragged-red fibers (MERRF). Moreover, there is a mild bias toward maternal transmission in migraine. Apart from clinical resemblance, there is some experimental evidence for mitochondrial dysfunction in migraine. There may be depression of respiratory chain enzyme activity in muscle and platelets, and magnetic resonance spectroscopy has revealed a defective energy metabolism in brain and muscle of migraine patients. There has not been a systematic study of mitochondrial DNA in migraine, however. We therefore analyzed the mitochondrial DNA in lymphocytes of 23 migraine patients with aura. Southern blot and polymerase chain reaction analysis of mitochondrial DNA failed to detect any large-scale deletions or point mutations at base pair 3243 (MELAS) and base pair 8344 (MERRF). Our data show that deletions of mitochondrial DNA and the most frequent point mutations of MELAS and MERRF syndromes are not common in migraine with aura. In particular, these data do not support the hypothesis that some cases of migraine may be monosymptomatic forms of a MELAS syndrome. We cannot exclude, however, that migraine may be associated with different point mutations of mitochondrial DNA or with mutations of autosomally coded respiratory chain subunit genes.