Background: Bradyarrhythmias may be presented as a serious emergency condition. The incidence, cause, and prognosis of the bradyarrhythmias requiring the temporary pacemaker (TP) are not well studied in Korea. Methods: In this retrospective study, TPs were inserted in 161 patients (M:F=74:87, mean age = 70 짹 12 years) at ER between Jan 1999 and Jun 2009. We divided the patients into two groups; group 1 [n= 80, treated with permanent pacemaker (PM)] and group 2 (n=81, treated without PM), and searched the clinical characteristics, causes and the ECG patterns of bradyarrhythmias in the two groups. Results: There were no significant differences in clinical characteristics between two groups. In Group 1, the common cause of bradyarrhythmias was idiopathic (n=74, 92.5%) and coronary artery disease (CAD) (n=6, 7.5%). The most common ECG pattern was complete AV block (56.3%). (Table 1) In Group 2, the causes of the bradyarrhythmias were as follows; CADs (n=46, 56.8%), drug related (n=15, 18.5%), hyperkalemia (n=9, 11.1%), unknown (n=8, 9.9%), and each of sepsis with hypotension, shock with ulcer bleeding, myocarditis in 1 patient (1.2%) respectively. Among the CAD group, the common ECG patterns were complete AV block (n=22, 44.3%), junctional escape (n=16, 30.8%) and sinus bradycardia (n=11, 21.2%). Conclusions: The most common underlying cause was idiopathic. However, in reversible cases, CAD was the main underlying cause. The evaluation of CAD is necessary in patients with severe bradyarrhythmia