Critically ill military trauma patients have been found to have a high incidence of psychological morbidity following their Intensive Care Unit (ICU) experience, including recall of significant auditory and visual hallucinations. It follows that this may be attributable to delirium, which has not been previously described in a young, previously fit population following trauma. The case-notes of 85 male patients (mean age 26 years), admitted to a single UK ICU following military trauma, were retrospectively assessed for delirium using DSM-IV criteria. Of the 993 ICU days assessed, 13.4% were deliriumpositive, with just over half of patients (51.8%) experiencing at least one day of delirium. On delirium-positive days, 69.2% received a documented intervention, with the majority of interventions (66.4%) being pharmacological, commonly with a sedative or anti-psychotic. Presence of delirium was significantly associated with severity of injury, assessed by Injury Severity Score (OR 1.037, 95% CI 1.003-1.072, p ¼ 0.031). Duration of ICU stay was significantly increased, from 4 to 8 days (p < 0.005), as was the duration of mechanical ventilation (for the 84.7% of patients who were ventilated) from 7 to 13 days (p < 0.005). Delirium is common in military trauma patients, despite their young age and premorbid fitness. A review of longer-term psychological outcomes should be considered.