The early detection and treatment of hypoxia is important to reduce patient morbidity in the accident and emergency department. At present, the commonly used methods all have practical difficulties in the urgent situations that prevail in the department. Pulse oximetry has recently become a method of choice in many anaesthetic and intensive care units for the continuous monitoring of oxygenation and the early detection of hypoxia. As similar conditions prevail in the accident and emergency department, we have attempted to evaluate its ease of use and the quality of information obtained in our department. Patients presenting with chest pain to an accident and emergency department have their oxygen saturation measured by the pulse oximeter finger probe prior to the commencement of oxygen therapy. After 5 min of oxygen therapy, the measurement was repeated. Our result showed that although no patients could be judged as hypoxic on clinical grounds the pulse oximeter showed, within 30 s of admission, that a number had an abnormal oxygen saturation. Continuous monitoring with the probe after the application of low flow oxygen therapy also aided in monitoring their treatment and this improvement was again easily and quickly recorded. Our experience shows that the pulse oximeter may be a useful tool for evaluating hypoxia and oxygen therapy in the accident and emergency department and we feel that we should be one of the groups who should reply in the positive to Zorab's question, 'Who needs pulse oximetry?' (Zorab, 1988).