Abstract: Background: A study published in 2000 found that the trauma team activation (TTA) system at Ulleval University Hospital (UUH), the trauma referral centre for half of the Norwegian population, had an undertriage of 15% and a positive predictive value (ppv) of 0,47. Female gender and old age were associated with undertriage.This led to implementation of a formal TTA system. Aim: Describe the efficiency of the current TTA system at UUH.Material and Methods: We conducted a prospective, trauma registry based study. Patients with ISS>15 or proximal penetrating trauma, were defined as seriously injured (SI). Undertriage was defined as the fraction of SI patients admitted without TTA and ppv was the fraction of TTA's where the patient was SI.Results: During the four-year period 2001 2004, 3087 patients were included, of which 1680 were SI. Of 2629 TTA's, 1222 were for SI patients, giving the system an undertriage of 27% and a ppv of 0,46. The primary admitted had an undertriage of 11% and a ppv of 0,41, compared to 53% and 0,78 for transferred patients. Age was still associated with undertriage.Conclusions: The introduction of a formal TTA system did not increase system efficiency and age was still associated with undertriage.