ALTHOUGH the initial traumatic damage to the skull and its contents may be slight, leakage of cerebrospinal fluid (CSF) through the nose, ear, or a compound fracture of the cranial vault may increase greatly the morbidity and possibility of death. The reported incidence of leakage of CSF in a series of patients with acute head injury depends upon an author's criteria for classification. Throughout the years my own patients with acute head injury have been subjected to periodic analysis, and to prevent diluting the series with patients who have sustained minor head blows, the following criteria were employed to categorize 2,194 patients as cases of acute head injury: (1) head trauma within the last month; (2) evidence of skull fracture (1,185 patients) by x-ray visualization of fracture, direct visualization of fracture, drainage of CSF from nose, ears, or compound fracture of cranial vault; pneumocranium; and/or (3) evidence of cerebral injury