Twelve patients (9 women, 3 men, mean age 26.8 +/- 5.02 years) with spontaneous isolated dissection of posterior cerebral artery (PCA) were studied. Eleven patients (92%) developed ischemic stroke, 1 patient (8%)--transient ischemic attack (TIA). All patients underwent magnetic resonance imaging (MRI) of the head and magnetic resonance angiography (MRA): 9 patients--a follow-up MRA, 3 patients--a single study. Local neurological symptoms (hemianopia, hemianestesia) developed suddenly (75%) during everyday patient's activity (83%) and were combined with headache on the side of dissection in 75% of patients. The main provoked factor was alcohol (67%), 25% had preceding respiratory infection. The initial cerebral angiography carried out in most cases within the first month of stroke demonstrated the occlusion (33%) or stenosis (67%) of PCA. The repeat MRA carried out on 2-3 months or more showed the improvement or normalization of blood flow in PCA (89%). In 1 (11%) patient the occlusive process progressed that correlated with headache increasing. A single MRA carried out in 48 days--6 months (3 patients) found the prolonged irregular stenosis (1), occlusion at P2 segment (1) and normal PCA appearance (1). At the whole, the prolonged irregular stenosis at least in one study, was found in a half of patients. None of patients had atherosclerosis, vasculitis, arterial hypertension or thrombophilia. Clinical manifestations of connective tissue weakness were seen in 67% of patients, hypotonia--in 67%, headache in the past history--in 67% and mitral valve prolapse--in 75%. In conclusion, spontaneous isolated dissection of PCA is one of the causes of ischemic stroke in young adults. The diagnosis is based on characteristic clinical manifestations and follow-up MRA. The development of dissection appears to be connected with arterial wall weakness.