Pulse oximetry has become one of the most commonly used tools in the clinical environment for assessing patients' oxygenation status. It is employed almost continuously in critical care areas and frequently in the general ward environment. Although it is a much better tool for determining hypoxia than the human eye, its use is limited if clinicians do not understand relevant physiological principles, such as the oxyhaemoglobin dissociation curve and the inherent limitations of the device. Furthermore, the risk for compromised patient safety is significant if clinicians fail to recognise the potential for false or erroneous readings. This paper explores the research which has examined clinicians' comprehension of pulse oximetry. Fourteen studies examining clinicians' knowledge of pulse oximetry were reviewed. These studies revealed significant knowledge deficits about pulse oximetry amongst nurses, doctors and allied health professionals, all of whom used this technology frequently. Alarmingly, those lacking an adequate understanding of pulse oximetry included senior, experienced clinicians. The studies were limited by their use of convenience sampling and small sample sizes. Further research is needed to better understand the significance of this problem and to examine how principles of pulse oximetry are taught to nurses and other health professionals at the undergraduate and postgraduate levels. Educators and clinicians alike must ensure that a safe level of knowledge for the use of pulse oximetry is maintained in order to ensure that patient outcomes are not compromised.