The objective was to compare secondary insults, particularly decreases in jugular bulb oxyhaemoglobin saturation (SjO(2)), during intensive care in patients with "poor" and "good" outcomes 12 months after traumatic brain injury. A prospective observational study of patients' physiological data collected each minute from multimodality monitoring was carried out. Patients had duration of physiological insults quantified as a percentage of their validated monitoring time (once invalid data due to technical reasons were removed). Treatment protocols were designed to minimise secondary insults by maintaining intracranial pressure (ICP) less than 20 mm Hg, and cerebral perfusion pressure (CPP) greater than 70 mm Hg, with prompt correction of hypoxia and pyrexia. Twelve months after injury patients' neurological function was assessed using the Glasgow outcome scale (GOS). A poor outcome was defined as GOS 1 to 3 (group 1) and a good outcome as GOS 4 and 5 (group 2). Seventy five patients (64 male), median age of 34 years (range 15 to 70), were studied. At 12 months 33 patients had a poor outcome (group 1), and 42 a good outcome (group 2). Group 1 spent proportionately more time with SjO(2) greater than 75% compared with group 2 (p<0.05), and more time with SjO(2) below 54% (p<0.04). Group 1 patients also spent proportionately more time with CPP less than 70 mm Hg than group 2 (p<0.04). Patients in group 1 were older (p<0.04) and had a lower postresuscitation Glasgow coma score (p<0.002). There was no difference between the groups for ICP, injury severity score, peripheral pulse saturation, and pyrexia. This study confirms that secondary insults, including an increased SjO(2), occur significantly more in patients with poor outcomes. More research into strategies to reduce the impact of secondary insults, including management of increased SjO(2), is required.