A selection of medical and nursing staff and anaesthetic technicians at work on a particular day at a regional Base Hospital were invited to complete a questionnaire to assess their knowledge of the principles of pulse oximetry. A 98.5% response rate (203 respondents) was achieved from staff in a broad cross section of hospital wards participating in the study. Most of the participants (nursing [N] 87%, medical [M] 91%, anaesthetic technicians [AT] 100%) used pulse oximetry regularly in their daily work. Less than half of the participants (N 36%, M 48% and AT 50%) felt they had adequate training in the use of pulse oximetry. Only 68.5% of participants correctly stated what pulse oximeters measure. Answers to the questions regarding the principles of pulse oximetry, potential errors, normal ranges or the physiology of oxygen haemoglobin dissociation varied but generally reflected limited understanding. As the use of pulse oximeters extends beyond the operating theatre and intensive care environment, appropriate staff education must ensure a basic understanding of the operating principles of the instrument.