The Advanced Trauma Life Support Course defines a primary and a secondary survey to rapidly identify life-threatening and associated injuries, respectively, in multiple trauma patients. However, circumstances during resuscitation, including multiple casualties, emergent operation, unconsciousness, etc., may interfere with this process. An initial review of our trauma registry data yielded a modest 2% incidence of missed injuries in a 90% blunt trauma population. In order to determine the true incidence of missed injuries, a tertiary survey was performed prospectively on all injured patients (N = 399) admitted during a recent 3-month period. After completion of the primary and secondary surveys (including appropriate roentgenographs), all injuries were listed in the trauma admission record. Patients were later reexamined immediately before ambulation or, in head-injured patients, upon regaining consciousness. All missed injuries were documented, including site and type of injury, reason missed, how identified, and attendant morbidity. Forty-one missed injuries were found in 36 patients (9%). These included: 21 extremity fractures, five spinal fractures, two facial fractures, five thoracic injuries, six abdominal injuries (including five splenic lacerations), and two vascular injuries. The most common reason for injuries to be missed was altered level of consciousness due to head injury or alcohol. Other reasons included severity of injury and instability requiring immediate operation, lack of symptoms at admission, technical problems, and low index of suspicion by the examiner. None of the missed injuries resulted in death. However, one missed injury caused serious disability and seven required operative correction.(ABSTRACT TRUNCATED AT 250 WORDS)