Early nutrition is advocated for patients with head injury to counter the postinjury hypermetabolic state. The gastric route of feeding often leads to vomiting and aspiration pneumonitis. This study was designed to identify the role of lower esophageal sphincter (LES) function in this complication. The LES function was assessed within 72 hours of admission in 16 patients with a head injury and a Glasgow Coma Scale (GCS) score less than 12 (range, 3-11). Other admission assessments included an APACHE II score of 11.7, Injury Severity Score (ISS) of 30.5, and a Revised Trauma Score (RTS) of 6.4. These studies were repeated 1 week postinjury in five patients. Dysfunction of the LES was present in all 16 patients; the average gastric-to-esophageal pressure difference was -0.49 mm Hg (range, -0.59 to 2.5) compared with a normal value of greater than 20 mm Hg. The five patients restudied at 1 week had a gastric-to-esophageal pressure difference of 13.3 mm Hg (range, -3.4 to 36.6 mm Hg). The single patient with a GCS score below 12 at 1 week had a low LES tone. These data show that LES dysfunction accompanies acute head injury and contributes to aspiration pneumonitis after early gastric feeding. Nutrition in patients with low GCS scores should be parenteral or via the jejunum.