Treatment bundles are associated with decreased mortality for severe sepsis/septic shock. In October 2012 the National Quality Forum endorsed Measure 500 (Severe Sepsis and Septic Shock: Management Bundle):A.Lactate measurementB.Blood cultures prior to antibioticsC.Broad spectrum antibioticsD.30ml/kg bolus of crystalloid for hypotension or lactate >=4 mmol/LE.Vasopressors for fluid resistant hypotensionF.CVP and ScvO2 measurement for persistent hypotension or initial lactate >=4mmol/L For compliance, A-C must be met <3 hrs of emergency department (ED) arrival (D-F <6hrs for shock only), independent of when patients meet diagnostic criteria. While antibiotic administration <1 hr of septic shock onset is associated with reduced mortality, little evidence validates defining time of presentation as ED arrival. If bundle is met <1hr after diagnostic criteria are met (appropriate care) but more than 3hrs from ED arrival (didn't initially meet criteria), providers will be non-compliant (“false negative”). To determine percentage of ED patients who did no meet diagnostic criteria <3 hrs from ED arrival and determine their impact on antibiotic administration <3 hrs from ED arrival (surrogate for bundle compliance). Design: retrospective descriptive analysis of a prospective cohort enrolled for quality assurance review. Setting: urban, tertiary, university ED with annual census of 39,000. Participants: all adult (age >= 18) ED patients with suspected severe sepsis/septic shock, September 5, 2012 - April 3, 2013. Severe sepsis / septic shock were defined in accordance with the 2012 Surviving Sepsis Campaign guidelines:•Known or suspected infection and•>=2 SIRS criteria and•End-organ dysfunction (severe sepsis) or refractory hypotension (shock). We report median time (IQR) from ED arrival to meeting diagnostic criteria. The primary outcome was percent (95% CI) of patients who did not meet diagnostic criteria <3 hrs of ED arrival. We also report compliance with antibiotic administration <3 hrs of ED arrival and <1 hr of severe sepsis/septic shock onset. Two hundred fifty-nine patients were suspected of having severe sepsis/septic shock during the study period. Median time from ED arrival until meeting diagnostic criteria was 71 min (35.5-130 min). 41 (15.8%, 95% CI 11.8-20.7) patients met diagnostic criteria >3hrs of ED arrival. Median time to antibiotics from ED arrival was 121 min (72 - 206 min). Overall, 67.6% (95% CI 61.7-73.1) received antibiotics <3 hrs after ED arrival. One hundred seventy patients (78%, 95% CI 72.6-82.7) met diagnostic criteria <3 hrs and received antibiotics <3hrs after ED arrival. One hundred sixty-six patients (64.1%, 95% CI 58.1-69.8) did so <1hr of meeting diagnostic criteria, regardless of ED arrival time. Notably, 29 patients (11.2%, 95% CI 7.6-15.7) received antibiotics <1hr of meeting diagnostic criteria, but not <3hrs after ED arrival (appropriate care but bundle non-compliant). ED arrival time inaccurately defines time of presentation for ED patients with suspected severe sepsis/septic shock. In this single center study, 15.8% of adult ED patients with suspected severe sepsis/septic shock did not meet diagnostic criteria < 3 hrs after ED arrival. If replicated more broadly, performance metrics need to account for this finding (ie, use time of meeting diagnostic criteria rather than ED arrival).