One of the most important aspects of caring for a critically ill patient is monitoring. Few would disagree that the most essential aspect of monitoring is frequent physical assessments. Complementing the physical examination is continuous monitoring of heart rate, respiratory rate, and blood oxygen saturation measured via pulse-oximetry, which have become the standard of care in intensive care units. Over the past decade one of the most controversial aspects of monitoring critically ill patients has been capnography. Although most clinicians use capnography to confirm endotracheal intubation, few clinicians use continuous capnography in the intensive care unit. This article reviews the medical literature on whether every mechanically ventilated patient should be monitored with capnography from intubation to extubation. There are numerous articles on capnography, but no definitive, randomized study has even attempted to address this specific question. Based on the available literature, it seems reasonable to use continuous capnography, for at least a subset of critically ill patients, to ensure integrity of the endotracheal tube and other ventilatory apparatus. However, at this point definitive data are not yet available to clearly support continuous capnography for optimizing mechanical ventilatory support. We hope that as new data become available, the answer to this capnography question will become clear.