OBJECTIVE: To investigate the relationships between intracranial pressure (ICP), cerebral perfusion pressure (CPP), and outcome after traumatic brain injury. MATERIAL AND METHODS: A retrospective analysis of prospectively recorded data from 429 patients after head injury requiring intensive treatment on the Neuroscience Intensive Annex and the Neuro Critical Care Unit, Cambridge, UK. ICP, CPP, and arterial blood pressure (ABP) were continuously recorded. Mean values of pressures were compared to outcome assessed at 6 months after injury (using the Glasgow Outcome Scale). RESULTS: The mortality rate was greater in those having mean ICP greater than 20 mmHg (17% below versus 47% above; p < 0.0001). The mortality rate was dramatically increased for CPP below 55 mmHg (81% below versus 23% above; p < 0.0001). For values of CPP greater than 95 mmHg, favorable outcome was less frequent (50% below versus 28% above; p < 0.033). The rate of severe disability showed the tendency to increase with CPP ( r = 0.87; p = 0.02), suggesting that a higher CPP does not help in achieving favorable outcomes. ICP was greater in those who died in comparison to those who survived (27 +/- 19 mmHg versus 16 +/- 6 mmHg; p < 0.10 - 7), and CPP was lower (68 +/- 21 versus 76 +/- 10 mmHg; p < 0.0002). There was no difference between mean ICP and CPP in good/moderate and severe disability outcome groups. CONCLUSION: High ICP is strongly associated with fatal outcome. Excessive CPP seems to reduce the probability of achieving a favorable outcome following head trauma.