ICP in 233 patients with severe head injuries was monitored utilizing a subarachnoid catheter technique. The relationships between initial ICP and GCS, between initial ICP and GOS, between maximal ICP and GCS, and between maximal ICP and GOS were examined statistically. The correlation was significant in each case, but particularly so between maximal ICP and GOS. Thus morbidity and mortality may be dependent upon maximal ICP. Catheterization of the subarachnoid space presents little difficulty using a Tuohy needle for epidural anesthesia as an introducer. Though the catheter is very fine (1.0 mm in outer diameter), failure of waveform occurred in only 2.1% of all patients. The procedure can be easily performed at the bedside, is safe, inexpensive, and useful for the management of severe head injuries. Meningitis was recognized in 4.7% of all patients.