Regional cortical cerebral blood flow (rCBF) and intracranial pressure (ICP) were monitored continuously with a combined thermal diffusion probe/ICP monitor in 12 patients (8 men and 4 women; mean age, 31 years; range, 7-65 years) with acute head injuries. The mean Glasgow Coma Scale score at admission was 6 (range, 4-12). The rCBF/ICP probes were placed during surgical procedures (n = 11) or in an intensive care unit (n = 1) for subdural hematomas (n = 7), cerebral contusions (n = 4), and an epidural hematoma (n = 1). No probe-related complications occurred. Reduced CBF often occurred and was often inversely proportional to elevations in ICP. Posttraumatic cerebral arterial vasospasm in one patient was detected by rCBF monitoring and confirmed by angiography. In 6 patients who progressed to brain death, rCBF patterns disappeared, which correlated with their clinical and electroencephalographic examinations. Several patients with severe, diffuse brain injuries and high ICP had hyperemic rCBF patterns. In 2 of these patients, increases in rCBF preceded rises in ICP, which implied loss of autoregulation as a mechanism in the development of malignant cerebral edema. This method of CBF monitoring has not yet been established for clinical decision making. The early detection of ischemic or hyperemic responses by continuous CBF monitoring could hasten intervention aimed at restoring adequate tissue perfusion. The technique could also serve as an index of the efficacy of therapeutic interventions and is suitable to gain more insight into the pathophysiology of head injury, especially the relationship of CBF to ICP.