BACKGROUND: Acute care surgery (ACS) model of care delivery has many benefits. However, since the ACS surgeon has limited control over the volume, timing, and complexity of cases, traditional metrics of operating room (OR) efficiency almost always measure ACS service as "inefficient." The current study examines an alternative method-performance fronts-of evaluating changes in efficiency and tests the following hypotheses: (1) in an institution with a robust ACS service, performance front methodology is superior to traditional metrics in evaluating OR throughput/efficiency, and (2) introduction of an ACS service with block time allocation will improve OR throughput/efficiency. METHODS: Operating room metrics 1-year pre-ACS implementation and post-ACS implementation were collected. Overall OR efficiency was calculated by mean case volumes for the entire OR and ACS and general surgery (GS) services individually. Detailed analysis of these two specific services was performed by gathering median monthly minutes-in block, out of block, after hours, and opportunity unused. The two services were examined using a traditional measure of efficiency and the "fronts" method. Services were compared with each other and also pre-ACS implementation and post-ACS implementation. RESULTS: Overall OR case volumes increased by 5% (999 ± 50 to 1,043 ± 46: p < 0.05) with almost all of the increase coming through ACS (27 ± 4 to 68 ± 16: p < 0.05). By traditional metrics, ACS had significantly worse median efficiency versus GS in both periods: pre (0.67 [0.66-0.71] vs. 0.80 [0.78-0.81]) and post (0.75 [0.53-0.77] vs. 0.83 [0.84-0.85]) (p < 0.05). As compared with the pre, GS efficiency improved significantly in post (p < 0.05), but ACS efficiency remained unchanged (p > 0.05). The alternative fronts chart demonstrated the more accurate picture with improved efficiency observed for GS, ACS, and combined. CONCLUSION: In an institution with a busy ACS service, the alternative fronts methodology offers a more accurate evaluation of OR efficiency. The provision of an OR for the ACS service improves overall throughput/efficiency.