&NA;Seventeen head‐injured patients with signs of brain stem compression at admission underwent emergency bilateral burrhole exploration before computerized tomographic (CT) scanning. After exploration of the epidural and subdural spaces, real‐time ultrasonography was performed intraoperatively to identify intraaxial hematomas. Epidural or subdural hematomas were identified surgically in 11 patients (65%) and immediately evacuated through a craniotomy; in 2 patients, bilateral subdural hematomas were removed. Ultrasonography showed no evidence of intracerebral mass lesions in 14 (82%) of the 17 patients, demonstrated extensive contusions of the temporal lobe in 2 patients (prompting partial lobectomy in both cases), and revealed a small intraparenchymal hematoma deep within the dominant hemisphere, which was not removed, in 1 patient. The sensitivity of ultrasound images for identifying intraparenchymal lesions was evaluated postoperatively by CT or autopsy. In 15 patients (88%), the results of ultrasonography were confirmed. In 2 (12%), CT scans showed small but significant lesions at the frontal pole missed by ultrasonography; one patient had a residual subdural hematoma, and the other a small intraparenchymal hemorrhage. These results confirm that patients with clinical evidence of brain stem compression soon after head injury often have extraaxial hematomas that can be readily identified by burr‐hole exploration. Although intraparenchymal hematomas are rare immediately after head injury, they can ususally be identified by intraoperative ultrasonography. This simple technique can reduce the risk of missing intractranial hematomas during emergency burr‐hole exploration and improve intraoperative decision making in this population of severely head‐injured patients. (Neurosurgery24:345‐347, 1989)