Poor core laboratory performance that causes delays in diagnosis and treatment is an impediment to optimal patient care, particularly in high-volume patient care areas such as the emergency department (ED). To evaluate the impact of laboratory performance on patient care outcomes, we obtained data from 11 hospitals related to laboratory test turnaround time (TAT) parameters and ED patient throughput. We observed that the average length of stay (LOS) in the ED correlated significantly with the percentage of total laboratory outliers (R2 = 0.75; P < .01) and to a lesser extent the TAT means (R2 = 0.66; P < .01). Furthermore, improvements in laboratory performance during the study were associated with concurrent decreases in ED LOS. Although in the past, laboratories have focused on TAT means for performance assessment, our observations suggest that a more appropriate method of benchmarking might be to aggressively set clinically driven TAT targets and assess performance as the percentage of results achieving this goal.