Based on the concept of the systemic inflammatory response syndrome (SIRS), a one-year retrospective study was carried out among a total of 2389 patients transported to the emergency room by ambulance. With respect to 351 patients who had all data necessary for evaluating SIRS criteria in 369 hospitalized patients, 200 met SIRS criteria within 24 hours of admission (24h-SIRS). The mortality rate for 24h-SIRS patients was significantly higher than that of non-SIRS patients. The mortality rate for 24h-SIRS patients increased sequentially as more SIRS criteria were met. In 235 patients who met SIRS criteria during hospitalization (overall-SIRS), 108 had sepsis. Of these, 60 developed severe sepsis, and 50 developed septic shock. The mortality rate for patients who had 3 or more consecutive days of SIRS was significantly higher than that for those with less than 3 consecutive SIRS days. Among 153 patients who had all data necessary for APACHEIII scoring within 24 hours of admission, the mortality rate for SIRS patients whose APACHEIII score was 50 or higher was 40.7%, significantly higher than that of other patients. In conclusion, SIRS criteria were demonstrated to be useful as indicators of severity and for predicting outcome in patients hospitalized through emergency services. Patients who met the following criteria were found to be a high-risk population among hospitalized emergency patients with SIRS: (1) Those who had three or more consecutive days of SIRS. (2) Those whose APACHEIII score was 50 or higher.