Ft is a common practice to position head-injured patients in bed with the head elevated above the level of the heart in order to reduce intracranial pressure OCP). This practice has been in vivid discussion since some authors argue a horizontal body position will increase the cerebral perfusion pressure (CPP) and therefore improve cerebral blood flow (CBF). However, ICP is generally significantly higher in the horizontal position. The aim of this study was to evaluate changes in regional microcirculation using tissue pO 2 (ti-p02), as well as changes in cerebral perfusion pressure (CPP) and intracranial pressure induced by changes in body position in patients with head injury. The effect of 0° and 30° head elevation on ti-p02, CPp, ICP and arterial blood pressure (MABP) was studied in 22 head injured patients during day 0-12 after trauma. The mean ICP was significantly lower at 30° head elevation than at 00 (74.1 + 8.6 vs. 19.9+8.3 mmHg). While MABP was unaffected by head elevation, CPP was slightly higher at 300 than at 0° (76.5+ -13.5 vs. 71.5+ 13.2 mmHg). However, regional ti-p02 was unaffected by body position (30° vs. 0°: 24.9+73.1 vs. 24.7 + 12.9 mmHg). fn add~tion, there was no change in the time course after trauma concerning these findings in the individLfal pati,ents. The data indicate that a moderate head elevation of 300 reduces ICP without jeopardizing regional cerebral microcirculation as monitored using a polarographic ti-p02 microcatheter. [Neural Res 1997; 19: 249-253]