Fifteen patients with acute cerebral infarct in the territory of the middle cerebral artery were examined with dynamic computed tomography (CT) to evaluate cerebral perfusion changes. Perfusion changes could be detected in 93% of the patients within a short period after the attack (the earliest instance was within 2 hours) and before any detectable morphologic change. The attenuation coefficient of the area of infarction showed a statistically significant difference in peak amplitude compared with that in the contralateral unaffected brain or with that in the control group (P less than .05). A delay in the time to peak in the affected side versus in the contralateral side was observed in six patients with stroke and ranged from 4.2 to 49.2 seconds with or without a change in peak amplitude. The clinical outcome in the patients correlated well with the initial perfusion change measured with dynamic CT scanning. The greater the difference in peak amplitude, the worse the residual neurologic defect. Patients with a prolonged time to peak (greater than 8 seconds) usually had poor clinical outcome. The whole dynamic study took 10-15 minutes more than a conventional CT study but provided more complete information as a basis for clinical treatment and an indication of clinical outcome.