Background Trauma team activation (TTA) is a wellrecognised standard of care to provide rapid stabilisation of patients with time-critical, life-Threatening injuries. TTA is associated with a substantial use of valuable hospital resources that may adversely impact upon the care of other patients if not carefully balanced. This study aimed to determine which of the two outcome measures would be a better standard for assessing the appropriateness of TTA at a paediatric centre: retrospective major trauma classification as defined within our state, and the use of emergency department high-level resources as recently published by Falcone et al (Falcone Interventions; FI). Methods Trauma registry data and patients charts between February 2011 and June 2013 were reviewed. Over-Triage and under-Triage rates for TTA, using both major trauma and FIs as outcome measures, were compared. Results Totallly, 280 patients received TTA, 243 met major trauma definition and 102 received one or more FIs. The rates of over-Triage and under-Triage were 39.7 (95 CI 35.0 to 44.6 ) and 30.5 (95 CI 26.2 to 35.2 ), when the major trauma definition was used as the outcome measure, and 67.5 (95 CI 62.2 to 72.5 ) and 10.8 (95 CI 7.9 to 14.8 ) when FI was used. Only 17.1 (95 CI 11.4 to 24.7 ) of the under-Triaged patients using the major trauma definition received one or more FIs. Conclusions Assessment of TTA appropriateness varied significantly based on the outcome measure used. FIs better reflected the use of acute-care TTA-related resources compared with the major trauma definition, and it should be used as the gold standard to prospectively assess and refine TTA criteria.