Missed injuries. The trauma surgeon's nemesis. The multiply injured trauma patient presents a diagnostic and therapeutic challenge: that of discovering all injuries while simultaneously proceeding with resuscitation and maintaining life. Many factors involved in the initial resuscitation of the multiply injured patient, such as altered level of consciousness, hemodynamic instability, or inexperience and diagnostic oversight, may lead to missed injuries. Injuries may be missed at any stage of the management of the trauma patient, including intraoperatively, and may involve all regions of the body. Established protocols in the initial management of the multiply injured patient, such as the primary and secondary surveys of the Advanced Trauma Life Support Course, will minimize the chance of missing immediately life-threatening injuries in the emergency department. A careful intraoperative approach must be used in all patients, but especially in those with hemodynamic instability, so that all areas are examined for possible injury, rather than concentrating simply on what is known to be injured. Use of the tertiary survey, a careful re-examination of the multiply injured trauma patient, especially when he or she awakes, will help detect injuries missed during the initial evaluation. Injuries will be missed. Rather than dismissing these as occurrences that happen only to the inexperienced or incompetent, one should approach the multiply injured trauma patient with both special alertness and the humility necessary to search for diagnostic oversights. This approach will lead to early discovery of missed injuries and will minimize the consequences. 