PURPOSE: It is important to begin a transfusion safely and appropriately as soon as possible in a hemorrhagic shock patient. A group O+ unmatched pack red blood cell (universal O+) transfusion may satisfy that requirement. We report our experiences with universal O+ to compare its usefulness for hemorrhagic shock patients with that of a matched pack red blood cell transfusion in the emergency department (ED). METHODS: This is a retrospective study. Patients who had systolic blood pressure of less than 90 mmHg or a pulse rate of more than 120 beats per minute in the ED were included, and their medical records were reviewed. The collected data were demographic data, vital signs, blood test results, time to transfusion, the amount of transfusion, complications, and diagnoses. We calculated the emergency transfusion score (ETS) based on the patients' medical records. RESULTS: Two hundred thirty-five patients were included. Forty-eight patients (36 trauma and 12 non-trauma patients) were transfused with a universal O+. These patients had less time to transfusion compared with the cross-matched transfusion groups (35+/-42 versus 170+/-187 minutes, p<0.001). There were no differences in complications between groups (p=0.076). Of the patients who were transfused with universal O+, 94.4% got more than 3 ETS. CONCLUSION: The universal O+ transfusion, compared with matched pack red blood cell transfusion, should be a useful treatment for ED hemorrhagic shock patient due to its having a shorter time to transfusion without an increase in complications.