['The objective was to evaluate the effect of arrival to the emergency department (ED) by emergency medical services (EMS) on time to initiation of antibiotics, time to initiation of intravenous fluids (IVF), and in-hospital mortality in patients with severe sepsis and septic shock.', 'The authors performed an evaluation of prospectively collected registry data of patients with a diagnosis of severe sepsis or septic shock who presented to an urban academic ED during a 2-year period from January 1, 2005, to December 31, 2006. Descriptive and multivariate analytic methods were used to analyze the data. Using unadjusted and adjusted models, out-of-hospital patients who presented to the ED by ambulance (EMS) were compared to control patients who arrived by alternative means (non-EMS). Primary outcomes measured were ED time to initiation of antibiotics, ED time to initiation of IVF, and in-hospital mortality.', 'A total of 963 severe sepsis patients were enrolled in the registry. Median time to antibiotics was 116 minutes for EMS (interquartile range [IQR] = 66 to 199) vs. 152 minutes for non-EMS (IQR = 92 to 252, p ≤ 0.001). Median time to initiation of IVF was 34 minutes for EMS (IQR = 10 to 88) and 68 minutes for non-EMS (IQR = 25 to 121, p ≤ 0.001). After adjustment for the Acute Physiology and Chronic Health Evaluation II (APACHE II) score, age, and initial serum lactate level, no significant differences in hospital mortality were seen (adjusted relative risk [aRR] for EMS vs. non EMS = 1.24, 95% confidence interval [CI] = 0.92 to 1.66, p = 0.16). The Cox proportional hazard ratio (HR) comparing EMS to non-EMS care after similar adjustment was HR = 1.27 for IVF (95% CI = 1.10 to 1.47, p = 0.004) and HR = 1.25 for antibiotics (95% CI = 1.08 to 1.44, p = 0.003).'] Does arriving by emergency medical services improve time to treatment endpoints for patients with severe sepsis or septic shock?