Medial medullary infarctions (MMI) were reported in less than 40 patients with satisfactory clinicotopographic documentation. We studied seven patients with MRI-proven acute MMI seen in two neurologic departments over a 5-year period (1990-1994). MMI represented less than 1% of ischemic strokes in the posterior circulation. Five patients had an infarction above the pyramidal decussation. All patients had contralateral hemiparesis and lemniscal sensory loss, accompanied by ipsilateral lingual palsy (Dejerine's syndrome) in three. Two patients had infarction below the pyramidal decussation, with ipsilateral hemiparesis and lemniscal sensory loss. Accompanying symptoms and signs of MMI were vertigo and nausea (n = 5), mild ipsi- or contralateral decrease in pain sensation (n = 6), headache (n = 4), ipsilateral limb ataxia (n = 6), contralateral truncal lateropulsion (n = 5), mild ipsilateral ptosis (n = 4), nystagmus (n = 4), dysarthria (n = 3), and somnolence (n = 2). Presumed causes of MMI were stenosis, occlusion or dissection of the ipsilateral vertebral artery (n = 5), and cardioembolism (n = 1). Outcome at 3 months was favorable in five patients. In conclusion, the clinical features of MMI are more heterogeneous than commonly thought, whereas its etiology seems fairly constant (vertebral artery disease).