This study examined whether a hospital-based helicopter trauma service led to 'overtriage' of patients back to the multispecialty base hospital. All accident-site triage decisions made during 1991 were studied. Seven of the 574 decisions (1·2 per cent) led to inappropriate movement of the patient to a specialist centre. Twenty-six decisions (4·5 per cent) were based on mechanism of injury alone and the possibility of overtriage by this method is discussed. A trained doctor can select the correct destination for a patient with trauma without inappropriately using the base hospital in preference to local centres.