Clinical neurological examination, computed tomography (CT) scan, cerebral angiography, and cerebral blood flow-single photon emission computerized tomography (CBF-SPECT) study have been performed in 39 patients with acute ischemic stroke within 6 h from the onset of symptoms. Seven of these patients were submitted to a second CBF study after an intravenous infusion of nimodipine. A greater CBF impairment was observed in patients with severe neurological deficit at entry, poor outcome, cerebral arterial occlusion, and large hypodensity on the CT scan performed 1 week after admission. In patients treated with nimodipine, a significant increase of CBF was detected at the periphery of the ischemic zone, indicating a potential action of this Ca antagonist on the "ischemic penumbra."