A 28-year-old female farmer, without vascular risk factors, developed a limited infarct of the pons, associated with a lymphocytic cerebrospinal fluid (CSF) pleocytosis. Titres of specific antibodies against Borrelia burgdorferi were high in serum and CSF. MRI confirmed an infarct in the territory of the medial pontine arteries, but angiography showed no evidence of cerebral angiopathy. Antibiotic therapy rapidly led to a return to normal of CSF cytology and serology. We suggest that Lyme disease is a possible cause of cerebral ischaemia.