Nine patients (six men, three women) with extracranial vertebral artery dissection are described. Their mean age was 39.1 years (range 17-66). In four cases dissection was "spontaneous"; in the other five cases there was a history of trivial trauma. Three patients had fibromuscular dysplasia, two were migraineurs, one had elastorrhexis. Treatment varied. Six received heparin, three acetylsalicylic acid or ticlopidine. Eight had good recovery. Two patients experienced recurrence when stopping acetylsalicylic acid. The pathogenesis of dissections and the distinction between spontaneous dissections and those associated with minor trauma are discussed.