Our hypothesis was that clinical outcomes are improved and cost and hospital length of stay (LOS) reduced as a result of the opening of a closed trauma intensive care unit (ICU). We conducted a cross-sectional study in a university-affiliated Level I trauma center. Our study population comprised trauma patients admitted to the ICU between June 1, 1996 and July 1, 1998 for at least 24 hours and with an Injury Severity Score (ISS) > 16 (excluding those with severe brain injury). The main outcome measures were changes in LOS and number of ventilator days, prevalence of complications, changes in patient charges, and hospital costs. Two hundred four patients were included [trauma ICU (TICU) 60, surgical ICU 144]. The two groups were not statistically different in age, ISS, mechanism of injury, infection rate, and mortality; however, the TICU patients had a lower number of ventilator hours (83.1 vs 100.0; P = 0.007), lower ICU LOS (9.4 vs 12.1 days; P = 0.06), and lower total hospital LOS (15.6 vs 22.3 days; P = 0.01). Although this was not of statistical significance TICU patients had lower hospital charges ($125,383 vs $152,994; P = 0.06) and lower cost per case ($42,306 vs $47,548; P = 0.35) for a net savings of $314,520 during the first 6 months of operation of the TICU. This study suggests that improved clinical outcomes and decreases in cost and LOS are directly related to the opening of a closed trauma ICU.