✓ A new classification of head injury based primarily on information gleaned from the initial computerized tomography (CT) scan is described. It utilizes the status of the mesencephalic cisterns, the degree of midline shift in millimeters, and the presence or absence of one or more surgical masses. The term “diffuse head injury” is divided into four subgroups, defined as follows: Diffuse Injury I includes all diffuse head injuries where there is no visible pathology; Diffuse Injury II includes all diffuse injuries in which the cisterns are present, the midline shift is less than 5 mm, and/or there is no high- or mixed-density lesion of more than 25 cc; Diffuse Injury III includes diffuse injuries with swelling where the cisterns are compressed or absent and the midline shift is 0 to 5 mm with no high- or mixed-density lesion of more than 25 cc; and Diffuse Injury IV includes diffuse injuries with a midline shift of more than 5 mm and with no high- or mixed-density lesion of more than 25 cc. There is a direct relationship between these four diagnostic categories and the mortality rate. Patients suffering diffuse injury with no visible pathology (Diffuse Injury I) have the lowest mortality rate (10%), while the mortality rate in patients suffering diffuse injury with a midline shift (Diffuse Injury IV) is greater than 50%. When used in conjunction with the traditional division of intracranial hemorrhages (extradural, subdural, or intracerebral), this categorization allows a much better assessment of the risk of intracranial hypertension and of a fatal or nonfatal outcome. This more accurate categorization of diffuse head injury, based primarily on the result of the initial CT scan, permits specific subsets of patients to be targeted for specific types of therapy. Patients who would appear to be at low risk based on a clinical examination, but who are known from the CT scan diagnosis to be at high risk, can now be identified. ✓ A new classification of head injury based primarily on information gleaned from the initial computerized tomography (CT) scan is described. It utilizes the status of the mesencephalic cisterns, the degree of midline shift in millimeters, and the presence or absence of one or more surgical masses. The term “diffuse head injury” is divided into four subgroups, defined as follows: Diffuse Injury I includes all diffuse head injuries where there is no visible pathology; Diffuse Injury II includes all diffuse injuries in which the cisterns are present, the midline shift is less than 5 mm, and/or there is no high- or mixed-density lesion of more than 25 cc; Diffuse Injury III includes diffuse injuries with swelling where the cisterns are compressed or absent and the midline shift is 0 to 5 mm with no high- or mixed-density lesion of more than 25 cc; and Diffuse Injury IV includes diffuse injuries with a midline shift of more than 5 mm and with no high- or mixed-density lesion of more than 25 cc. There is a direct relationship between these four diagnostic categories and the mortality rate. Patients suffering diffuse injury with no visible pathology (Diffuse Injury I) have the lowest mortality rate (10%), while the mortality rate in patients suffering diffuse injury with a midline shift (Diffuse Injury IV) is greater than 50%. When used in conjunction with the traditional division of intracranial hemorrhages (extradural, subdural, or intracerebral), this categorization allows a much better assessment of the risk of intracranial hypertension and of a fatal or nonfatal outcome. This more accurate categorization of diffuse head injury, based primarily on the result of the initial CT scan, permits specific subsets of patients to be targeted for specific types of therapy. Patients who would appear to be at low risk based on a clinical examination, but who are known from the CT scan diagnosis to be at high risk, can now be identified.