Overcrowding and prolonged patient length-of-stay (LOS) in emergency departments (EDs) are growing problems. We evaluated the impact of implementing a rapid whole blood quantitative D-dimer test (Biosite Triage, Biosite Diagnostics, San Diego, CA) in our ED satellite laboratory on 252 patients before vs 211 patients after implementation. All patients also underwent testing with the existing central laboratory method (VIDAS D-dimer, bioMérieux, Durham, NC). D-dimer turnaround time (from blood draw to result) decreased approximately 79% (approximately 2 hours vs 25 minutes). The mean ED LOS declined from 8.46 to 7.14 hours (P = .016). Hospital admissions decreased 13.8%, ED discharges increased 7.3%, and the number of patients admitted for observation increased 6.4% (P = .005). No difference in the utilization of radiologic studies was observed (P = .86). At 3 months' follow-up, none of the after-implementation patients with negative D-dimer results were admitted for subsequent venous thromboembolic disease. The rapid D-dimer test was associated with a shorter ED LOS and fewer hospital admissions.