Major trauma is any injury that has the potential to cause prolonged disability or death. There are many causes of major trauma, blunt and penetrating, including falls, motor vehicle collisions, stabbing wounds, and gunshot wounds. Depending on the severity of injury, quickness of management and transportation to an appropriate medical facility (called a trauma centre) may be necessary to prevent loss of life or limb. The initial assessment is critical, and involves a physical evaluation and also may include the use of imaging tools to determine the types of injuries accurately and to formulate a course of treatment.

In 2002, unintentional and intentional injuries were the fifth and seventh leading causes of deaths worldwide, accounting for 6.23% and 2.84% of all deaths. For research purposes the definition often is based on an injury severity score (ISS) of greater than 15.

Primary physical examination is undertaken to identify any life-threatening problems, after which the secondary examination is carried out. This may occur during transportation or upon arrival at the hospital. The secondary examination consists of a systematic assessment of the abdominal, pelvic, and thoracic areas, a complete inspection of the body surface to find all injuries, and a neurological examination. Injuries that may manifest themselves later, may be missed during the initial assessment, such as when a patient is brought into a hospital's emergency department. Generally, the physical examination is performed in a systematic way that first checks for any immediate life threats (primary survey), and then taking a more in-depth examination (secondary survey).

Persons with major trauma commonly have chest and pelvic x-rays taken, and, depending on the mechanism of injury and presentation, a focused assessment with sonography for trauma (FAST) exam to check for internal bleeding. For those with relatively stable blood pressure, heart rate, and sufficient oxygenation, CT scans are useful. Full-body CT scans, known as pan-scans, improve the survival rate of those who have suffered major trauma. These scans use intravenous injections for the radiocontrast agent, but not oral administration. There are concerns that intravenous contrast administration in trauma situations without confirming adequate renal function may cause damage to kidneys, but this does not appear to be significant.

In the U.S., CT or MRI scans are performed on 15% of those with trauma in emergency departments. Where blood pressure is low or the heart rate is increased—likely from bleeding in the abdomen—immediate surgery bypassing a CT scan is recommended. Modern 64-slice CT scans are able to rule out, with a high degree of accuracy, significant injuries to the neck following blunt trauma.