Three hundred cases of polytrauma were investigated to evaluate the reliability of the Lindsey severity index. This simplified injury score can be used by paramedics or low-skilled emergency practioners to obtain a correct screening of patients and an initial prognosis on the basis of a simple injury severity scale. An evaluation by the Lindsey index was done in the field and at the emergency care unit. Results compare the final status of the patient which was obtained using the Patel score, derived from the patient's chart after his discharge. The Lindsey index demonstrated a correct assessment of the patient's status in 60% of the cases at the scene of the accident and 77% in the emergency unit. Most of the errors were due to underevaluations of the skull and spinal trauma. Patel's scale emphasizes locomotor sequellae, while skeletal injuries seldom provide life-threatening events, widely considered in the Lindsey index. Lindsey's index is a simple and reliable tool for initial assessment and a useful method of teaching.