The purpose of the present study was to determine blood-brain barrier (BBB) permeability, regional cerebral blood flow (rCBF) and regional cerebral plasma volume (rCPV) in the period immediately after head injury, and thereby to evaluate the effects of vascular factors in the pathophysiology of traumatic brain injury. Male Sprague-Dawley rats (350-450 g) anesthetized with 1.0-1.5% halothane were subjected to an impact acceleration closed head injury at the moderate level. BBB permeability (n = 5), rCBF (n = 8) and rCPV (n = 9) were measured by quantitative autoradiographic techniques using 14C-alpha-aminoisobutyric acid (AIB), 14C-iodoantipyrine and 14C-sucrose, respectively. Intravenous administration of each radiotracer was simultaneous with the traumatic impact. At 10 min after injury, BBB permeability, the transfer constant for AIB, was less than 0.1 ml/kg/min for all regions except for those with a relatively leaky BBB. At 30 s after injury, a significant and heterogeneous increase in rCBF was observed at 9 subcortical regions (p < 0.05). RCPV increased significantly in the frontal cortex, parietal cortex, thalamus, and hypothalamus (p < 0.05). In our closed head injury model without severe hypertension, BBB disruption did not occur immediately after trauma. Vascular responses in the period immediately after trauma may result from the derangement of cerebral autoregulation.