Bloodstream infection (BSI) is recognized as an important infectious complication of major trauma. However, its occurrence, the risk factors contributing to its development, and its outcomes have not been well described.Cohort with linkage of regional trauma and microbiology databases.Adult trauma patients with injury severity score (ISS) > or = 12 admitted to a regional trauma centre during a 33-month period.Of 1797 victims of acute trauma identified (median ISS 20; interquartile range [IQR] 16-25), 71 (4%) had 77 episodes of BSI, for an overall rate of 2.9 per 1000 hospital days. BSI in the majority of patients (37 of 72, or 52%) had onsets within the first week of hospitalization; 7 (10%) patients had community-acquired BSI (onset within 2 d). Independently associated with the development of nosocomial BSI were higher ISSs (odds ratio [OR] 1.04, 95% confidence interval [CI] 1.02-1.07); requirement for ICU admission (OR 7.06, CI 3.38-14.75); and burns (OR 5.75, CI 2.16-15.30). Although trauma-related BSI was a predictor of increased in-hospital case fatality (15/71 v. 208/1726; relative risk 1.75, CI 1.10-2.78), it was not an independent predictor of death.In our series, 1 in 25 major trauma cases was complicated by BSI. The infection occurred within the first week after injury in over half of our cases. Knowledge of the epidemiology of these infections will be important for planning preventive or early therapeutic efforts.