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A series comprising 12 patients who had intraarterial local fibrinolysis in the carotid territory is reported. A classification is proposed that divides the different types of occlusions into three groups on the basis of angiographic location. Group 1 (two cases) comprises occlusion of the extra- and/or intracranial carotid artery with patency of the circle of Willis and the lenticulostriate arteries. In this group, there is no brain infarction, the CT findings are normal, and the clinical signs are mainly hemodynamic and intermittent. Fibrinolysis may be performed late and rather safely and completed by surgery or angioplasty of the neck vessel stenosis responsible for the occlusion. Group 2 (five cases) comprises occlusions of the cortical arteries without involvement of the lenticulostriate arteries. The mechanism of the occlusion can be hemodynamic or embolic. Group 3 (five cases) comprises occlusions of intracerebral arteries involving the lenticulostriate arteries. In groups 2 and 3 with brain infarction, fibrinolysis will only be able to restore viability of the area of cerebral tissue surrounding the infarction (penumbra). The time factor is particularly critical in group 3 because lenticulostriate arteries are terminal vessels whose revascularization may induce hemorrhages with increasing frequency as the occlusion time is prolonged. The time factor is less critical in group 2 because collaterals make the ischemia less severe in the infarcted area and the vital and functional consequences of hemorrhage are not as serious as in group 3 because of the location. In this series, all the symptomatic complications of hemorrhage (two cases) occurred in group 3, in patients treated later than 6 hr after clinical onset. Given the time delay inherent in performing CT and angiography and in making the medical decision, it is considered dangerous to undertake fibrinolytic therapy in group 3, unless it can be started before 4 or 5 hr after clinical onset.