Physiological measures of injury are used as triage tools to identify patients that require treatment in trauma centres. The Pre-Hospital Index (PHI) is based on systolic blood pressure, pulse, respiratory rate, (level of) consciousness, and presence of penetrating injury. The present study evaluated the validity and internal consistency of the PHI. The study was based on 628 patients assessed by physicians at the scene. Mean age was 38.7 years (SD = 24.8), and 65% were male. Motor vehicle collisions caused the injury for 45%. The majority had head/neck (56%) and extremity (45%) injuries. Mean PHI was 4.62 (SD = 5.77), 40% had a PHI of zero, 6% between 1 and 3, 32% between 4 and 7, and 21% greater than 7. The associations between PHI and rates of hospital admission, surgery, ICU treatment, mortality, duration of hospitalization, and length of ICU stay were significant (p 3 had 83% sensitivity and 67% specificity for identifying these patients. Internal consistency of the PHI variables was above the acceptable limits. This study has shown that the PHI is a valid and reliable physiological measure of injury severity and field triage tool.