Eighteen of twenty patients with subclavian or innominate artery obstruction experienced episodes of transient cerebral arterial insufficiency; one patient suffered acute stroke and coma; all patients had angiographic evidence of subclavian or innominate artery obstruction; and most were shown to have retrograde flow in a vertebral artery. Two clinical patterns were apparent by arteriographic studies. Six patients had single lesions of a subclavian artery resulting in centrifugal cerebral ischemia. A second group of 14 patients had other significant lesions of either the carotid or vertebral-basilar arterial systems. Carotid-subclavian bypass or aorto-subclavian bypass are the preferred methods of reconstruction of subclavian obstructions. Of these two approaches, the extrathoracic procedure is preferable.