Giant cell arteritis (GCA) is known to affect the extracranial part of the vertebral arteries. Bilateral vertebral artery occlusion (BVAO) is a rare but serious neurologic condition. We report 3 patients with autopsy-proven (2 patients) or clinically diagnosed (1 patient) GCA causing BVAO. A review of the literature concerning BVAO revealed 5 other cases of BVAO resulting from GCA and 110 cases with underlying arteriosclerotic disease. Our 3 patients (mean age, 66 yr; range, 60-78 yr) with BVAO resulting from GCA all had initial severe headache followed by the onset of stepwise progressive, partly side-alternating neurologic deficits due to bilateral infarctions in the vertebrobasilar circulation territory. This course, more accelerated in BVAO due to GCA than in BVAO of arteriosclerotic origin, seems to be a typical, if not particular, clinical syndrome. BVAO was the first clinical manifestation of GCA in 1 of our patients and in 1 published case. From a clinical view, BVAO resulting from GCA differs from BVAO of arteriosclerotic origin by the much higher mortality rate (75% versus 19%, respectively), the presence of headache (100% versus 22%), fever (50% versus 0%), and elevated erythrocyte sedimentation rate (ESR in all GCA cases >45 mm/h; no data in the arteriosclerotic patient group), but not by the neurologic signs themselves. Therapy of BVAO resulting from GCA is purely empiric. In view of the serious prognosis, we propose treatment with intravenous high-dose glucocorticoids and additional immunosuppression with cyclophosphamide; the use of anticoagulation depends on the individual patient's estimated risk-benefit profile. Although BVAO due to GCA is rare, physicians and especially rheumatologists or neurologists should be aware of this entity because of its high mortality in patients without immediate introduction of a high-dose immunosuppressive therapy. Suspicion of GCA should arise in a patient aged over 50 years with no other vascular risk factors suffering from bilateral symptoms of ischemia in the vertebrobasilar territory, with a quickly progressing stepwise course and with headache, fever, or history of myalgia. ESR and temporal artery biopsy should be performed without delay. Early diagnosis of GCA is necessary for immediate initiation of intensive antiinflammatory and immunosuppressive treatment, without which progressive deterioration and systemic involvement are likely to be fatal.