The purposes of this study were to evaluate the clinical utility of a colorimetric end-tidal CO2 (ETCO2) detector in confirming proper endotracheal intubation in patients requiring emergency intubation, to determine if this new device can be used as an adjunct to judge the effectiveness of cardiopulmonary resuscitation (CPR), and to determine whether the device can predict successful resuscitation from cardiopulmonary arrest. We studied prospectively 110 patients requiring emergency intubation for either respiratory distress (53 patients) or cardiopulmonary arrest (57 patients) by recording the color range of the indicator after the initial intubation. In patients who suffered a cardiopulmonary arrest, the color range was also recorded during CPR after the endotracheal tube was confirmed to be in the tracheal position and perfusion optimized, and at the moment CPR was stopped. The ETCO2 detector was 100% specific for correct endotracheal intubation in all patients. It was also highly sensitive (0.98) for correct endotracheal intubation in patients with respiratory distress. However, it was not sensitive (0.62) in patients with cardiopulmonary arrest and low perfusion. The sensitivity improved (0.88) when we used the ETCO2 range obtained after attempts to increase perfusion. A low ETCO2 color range in 19 patients undergoing CPR was interpreted as low cardiac output and prompted the physicians to attempt to increase perfusion. Of the patients who underwent CPR, no patient whose ETCO2 level remained less than 2% was successfully resuscitated. Those patients who had an ETCO2 level ≥2% had a significantly higher incidence of successful resuscitation. We conclude that the colorimetric ETCO2 detector is reliable and provides reassurance of correct endotracheal tube placement in patients requiring emergency intubation for respiratory distress. This device helps identify patients with low perfusion during CPR and is a useful prognostic indicator of successful short-term resuscitation.