Optimal management of British military personnel injured in Afghanistan is best achieved in the United Kingdom; therefore aeromedical evacuation (AE) is arranged, often within the first 24 hours for the most severely injured casualties. However, early aeromedical evacuation carries its own risks, which must be considered prior to emplaning any casualty. The study aim was to investigate whether changes in tissue oxygenation occur in military casualties during aeromedical evacuation. Near infra-red spectroscopy was used in a series of studies designed to test the sensitivity of the tissue oxygen saturation monitoring technique in volunteers exposed to simulated altitude and simulated hypovolaemia. Changes in tissue oxygen saturation readings were detected in the volunteers, so an observational study was undertaken to determine whether changes in tissue oxygen saturation occur in military trauma casualties during aeromedical evacuation. Whilst the majority of casualties did not demonstrate any significant change in readings, some casualties did demonstrate reduced tissue oxygen saturation readings during their flights, although these changes were not reflected in systemic physiological monitoring techniques. Having identified that changes do occur, further work is required to investigate the cause, significance and outcome of these changes in order to fully appreciate the findings of the current study.