We treated five patients with hemispheric ischemic stroke with intravenous recombinant tissue plasminogen activator (rtPA), within 3-6 h after stroke onset. Regional cerebral blood flow was evaluated with single photon emission computed tomography (rCBF-SPECT) before and after treatment. One patient with aphasia and a moderately severe hemiparesis, who had a small flow deficit, was treated 5 h and 30 min after the onset of his stroke and had a prompt and complete recovery. The post treatment rCBF-SPECT showed normal flow. One patient with a very large flow deficit died of transtentorial herniation. In three other patient clinical condition remained unchanged, in one of them despite restoration of flow, demonstrated by transcranial doppler examination. In all these patients the rCBF-SPECT remained abnormal. rCBF-SPECT is a valuable tool in the explanatory analysis of fibrinolytic treatment in ischemic stroke.