For 51 patients suffering from traumatic brain injury (GCS < 9), we compared the prognostic value of critical parameters derived from neuromonitoring of intracranial pressure (ICP), cerebral perfusion pressure (CPP) and brain tissue oxygenation (PiO2) during different time periods after trauma (< or = 12, < or = 24, < or = 48, < or = 72 and < or = 96 h). For patients with good outcome (GOS = 4-5, n = 30) the proportion of critical ICP values (> 40 mmHg) was about 0.2% during all time periods. The corresponding proportions for patients with bad outcome (GOS = 1-3, n = 21) rose from 0.2% to 4.7% during increasing time periods. The frequency of critical ICP values was significantly related to outcome (p < 0.001) for time periods > 48 h after trauma. Differences of critical CPP (< or = 50 mmHg) and hypoxic PiO2 (< or = 5 mmHg) between both outcome groups were less pronounced and for both parameters significant relations to outcome were only obtained for the longest time period (< or = 96 h, p < or = 0.05). Higher thresholds for CPP (< or = 60 mmHg, < or = 70 mmHg) did not reveal any relation to outcome. For all neuromonitoring parameters significant relations between the frequency of critical values and outcome could be determined. Critical ICP values provide the earliest and highest prognostic power, while critical CPP and hypoxic PiO2 only showed prognostic power in later time periods.