To determine whether a positive blood alcohol level (BAL) affects morbidity and mortality at a Level I trauma center, a retrospective review of trauma patients 18 years of age and older was performed. There were 7985 trauma patients and 8 per cent (645) had a positive BAL. BAL(+) patients had lower Injury Severity Score (ISS) (8 vs 11, P < 0.01), lower rate of penetrating injury (9 vs 25%, P < 0.01), and were older (38 vs 32 years, P = 0.01). Overall there were 559 deaths (7%); (1% mortality in BAL(+) patients and 7% in BAL(-) patients; P < 0.0001). There were 352 (4.4%) complications with similar rates among BAL(-) and (+) patients. On univariate analysis, a positive BAL was inversely associated with death (OR, 0.17) as was blunt trauma (OR, 0.29), whereas older age (OR 1.009) and increased ISS (OR 1.13) were associated with death. On multivariable analysis, after adjusting for age, ISS, and mechanism of injury, a positive BAL remained protective against death (OR 0.35) as did blunt trauma (OR 0.2). Age (OR 1.04) and increased ISS (OR 1.19) were associated with mortality. In conclusion, a positive BAL was associated with a decreased mortality risk in trauma patients, which persisted after adjusting for multiple confounding variables.