The hypothesis that high level on-the-field ATLS could influence mortality in severe trauma patients was tested by means of a prospective study. During a 7 month period, data of all the victims of severe involuntary trauma (road traffic accidents, work and sport accidents) in 3 Provinces of north-east Italy were entered in a database and analysed. The whole area is covered by a single emergency service which has direct control over all the ambulances and the Emergency Helicopter Service (EMHS). The area concerned by the study has a surface of 7,300 kmq with a population of 1 million inhabitants and is served by 12 first level hospitals and 4 second level institutions (trauma centres). All the patients who were still alive at the time of arrival of the first rescuers were considered, but only severe trauma patients with ISS > 15 were enclosed into the study. All the patients were followed up to their discharge from the ICUs (end point). There were three different rescue approaches: 82 Patients (GROUP A) were rescued by EMTs with BLS training, transported to the nearest level 1 hospital for stabilisation and subsequently transferred to a trauma center; 98 Patients (GROUP B) were rescued by EMTs and directly transported to a trauma centre which was the nearest institution; 42 Patients were rescued on the scene by the EMHS team including an anaesthesiologist with 10 years experience in trauma care and directly transported to a trauma centre after full on-the-field stabilisation (GROUP C) RESULTS: 222 severe trauma patients (ISS > 15) were considered. Mean ISS was 35.1 +/- 18.2 in group A, 33.4 +/- 19.6 in group B and 36.0 +/- 17.8 in group C. 67 patients died previous to ICU discharge (31%). 31 over the 82 pts in Group A (38%) died. 23 of them died even before reaching the trauma centre. The mean time elapsed between the first emergency call and the arrival at the trauma centre was 162 min (90'-300'). Mean ICU stay for patients who survived was 15 days. In Group B 31 over 98 patients (32%) died before ICU discharge. The mean time between the emergency call and hospital admission was 27'. Mean ICU stay for patients who were discharged, was 13 days. 5 over 42 patients rescued by the EMHS (Group C) died, none of them in the pre-hospital setting. Stabilisation included tracheal intubation in 34 cases (81%) and thoracic drainage in 6 (14%). All the patients arrived at the hospital with 2 i.v. line. The average amount of infused fluids were 600 mls of colloids and 810 mls of crystalloid. 13 patients with hypotension received and average of 1000 mls of colloids and 1200 mls of crystalloid. The average time elapsed between the emergency call and the final admission to the definitive care institution was 55'. Mean ICU stay was 11 days. Mortality rate in this group was 12%, significantly lower than in group A (p < 0.005) and group B (p < 0.05).