Oxygen plays a pivotal role as a nutrient to the brain. Monitoring partial pressure of oxygen (ptO2) has been shown to correlate with outcome after brain injury if certain tissue-ptO2-goals can be achieved. Oxford Optronix has recently developed a new fiber-optic based sensor (MPBS) with a large tissue sampling volume and long-term stability up to 10 days. Direct comparison of the MPBS sensor with the Licox system was performed using an in-vitro and in-vivo model. No statistically significant differences between the MPBS and the Licox sensor in different settings were found. The response times to a sudden drop in ptO2 was faster for the MPBS than for the Licox probes (time of 80% signal change; 65 +/- 11 vs 110 +/- 14 s; p<0.05).