The authors studied 86 consecutive patients admitted to the ICU after severe head trauma. Of these, 19 nondiabetic patients developed persistent nonketotic hyperglycemia (NKH), defined as plasma glucose greater than 270 mg/dl (15 mM/L), 1.7 ± 1.1 (SD) days after injury. When NKH occurred, all patients were in very deep coma (Glasgow Coma Scale score 3), and when intracranial pressure (ICP) was measured (12 patients), its mean value was 59.8 ± 20.4 mm Hg. Although 11 of 19 patients had associated diabetes insipidus (DI), NKH was not related to increased fluid and glucose loading. All patients with NKH died (mean time of survival after NKH was 2.1 ± 1.4 days) in contrast to a 17.1% early mortality rate in patients with severe head injury without NKH. The authors could not show a direct correlation between the height of ICP and the level of blood glucose.