Background: It is difficult to evaluate the effectiveness of ongoing cardiopulmonary resuscitation(CPR) Recent stud- ies suggest that continuous end-tidal carbon dioxide(ETCOz) monitaring may be useful non-invasive indicator of CPR The purpose of this study is to determine whether ETCO monitoring during CPR could be used as a prognostic indi- cator of resuscitation and survival, Method: A prospective, dinical study was performed fiom May 1997 to April 1998 at the department of emergency medidne, Ewha Womans University Mokdong haspital All patients were immediately connected to mainstream cap- nometer sensor between the tube and the bag after endotracheal intubation using infrared capnometer Result: The study included 70 patients (39 were men) with a mean age of 55±16 years 37 patients with retum of spontaneous circulation(ROSC) had higher maximal ETCO during CPR than 33 patients without ROSC (26.9±19.4 vs 10.2±9.OmmHg, P=0001) The ETCO2 was not significantly different in relation to age, gender, initial rhythm, and survival time after ROSC. But there was significant diffaent in immediate cause of arrest in ROSC group(P=0.0016). When maximal ETCO2 was less fhan 10mmHg, we observed sensitivily of 83.8%, 'specificity of 54.5% in predicting ROSC There were 6 patients with ROSC in spite of maximal ETCO2 was less than 10mmHg Condusion : Continuous ETCO2 monitoring during CPR may be useful, noninvasive, and valuable predictor of suc- cessful resuscitation and survivaI fiom cardiac arrest But ETCO2 should not be used as a single indicator for the with- drawal of CPR