BackgroundThe guidelines for Level I trauma center verification require 1,200 admissions per year. Several studies looking at the relationship between hospital volume and outcomes after injury have reached conflicting conclusions. The goal of our study was to examine the relationship between patient volume and outcomes (mortality and length of hospital stay) in California’s trauma centers.MethodsData for patients ≥ 18 years old admitted after injury (n = 98,245) to a Level I or II trauma center (n = 38) in 1998 and 1999 were obtained from the Patient Discharge Data of the State of California. Hospital volume was derived from the annual number of admissions per center, and covariates including age, sex, mechanism of injury, Injury Severity Score, and trauma center designation were analyzed.ResultsHospital volume was not a significant predictor of death or length of hospital stay. More severely injured patients appeared to have worse outcomes at the highest volume centers.ConclusionIn our study, hospital volume was not a good proxy for outcome. Low-volume centers appeared to have outcomes that were comparable to centers with higher volumes. Perhaps institutional outcomes rather than volumes should be used as a criterion for trauma center verification.