Computerized tomography scanning has shown that acute traumatic intracranial hematomas are more common than was previously realized, but whether all hematomas must be removed remains controversial. About half of this series of 26 patients who were not clinically deteriorating and who were initially managed without operation had to undergo hematoma removal because they subsequently deteriorated. Features present at the time of diagnosis (age, type and site of hematoma, presence of focal signs, level of responsiveness, and degree of midline shift) were not helpful in predicting that operation would be needed. The only discriminatory factor was the level of intracranial pressure (ICP). All the patients with ICP greater than 30 mm Hg deteriorated and required operation, but only one patient whose ICP was less than 20 mm Hg deteriorated. Half the patients with ICP between 20 and 30 mm Hg did not require an operation. Intracranial pressure monitoring can, therefore, be useful in managing patients with an occult intracranial hematoma.