The critical care community has used standard criteria for defining the sepsis syndromes and organ dysfunction for more than 15 years; however, these criteria are not well validated in the emergency department (ED) setting. The study objectives in our ED population of patients admitted to the hospital are to determine the prevalence of the sepsis syndromes, quantify inhospital mortality and 1-year survival associated with the sepsis syndromes, and assess the inhospital and 1-year survival associated with organ dysfunctions. This was a prospective, observational, cohort study from February 1, 2000, to February 1, 2001 in an urban university hospital ED with 50,000 annual visits. There were 3,102 (96% of eligible) consecutive adult patients (aged 18 years or older) with suspected infection (as indicated by the clinical decision to obtain a blood culture) who were enrolled. Patients were screened for systemic inflammatory response syndrome (SIRS) (2 or more indicators of inflammatory response), sepsis (SIRS plus suspected infection), severe sepsis (sepsis plus organ dysfunction), septic shock (sepsis plus hypotension refractory to an initial fluid challenge), and number of organs with acute dysfunction. Main outcome measure was inhospital and 1-year mortality. Overall inhospital mortality was 4.1% and 1-year mortality was 22%. The inhospital mortality rates were suspected infection without SIRS 2.1%, sepsis 1.3%, severe sepsis 9.2%, and septic shock 28%. Compared to suspected infection without SIRS, adjusted risks of inhospital mortality were severe sepsis (odds ratio [OR] 4.0; 95% confidence interval [CI] 2.6 to 6.3) and septic shock (OR 13.8; 95% CI 6.6 to 29). Severe sepsis (OR 2.2; 95% CI 1.8 to 2.6) and septic shock (OR 3.5; 95% CI 2.3 to 5.3) also predicted 1-year mortality. The presence of SIRS criteria alone had no prognostic value for either endpoint. Each additional organ dysfunction increased the adjusted 1-year mortality hazard by 82% (pulse rate: 1.82, 95% CI 1.7 to 2.0). Immediate identification of acute organ dysfunction in ED patients with suspected infection may help select patients at increased short- and long-term mortality risk. SIRS criteria offered no additional prognostic value, whereas each additional organ dysfunction increased the 1-year mortality risk.