Background: Base Deficit (BD) and lactate have been used as indicators of shock and resuscitation. This study was done to evaluate the utility of BD and lactate in identifying shock and resuscitative needs in trauma patients. Methods: A prospective observational study was performed from 3/2014-12/2018. Data included demographics, admission systolic BP, ISS, BD, lactate, blood transfusion, and outcomes. BD and lactate were modeled continuously and categorically and compared. Results: 2271 patients were included. BD and lactate were moderately correlated (r(2) = 0.63 p < 0.001). On univariate regression, BD and lactate were associated with transfusion requirement and mortality (p < 0.001), but on multivariate regression, only BD was associated with transfusion requirement and mortality (OR = 1.2, p < 0.001; OR = 1.1, p < 0.001, respectively). BD discriminated better than lactate for hypotension, higher ISS, increased transfusion requirements and mortality. Conclusions: Admission BD and lactate levels are correlated following injury, but BD is superior to lactate in identifying shock, resuscitative needs and mortality in severely injured trauma patients. (c) 2020 Elsevier Inc. All rights reserved.