This paper evaluates the effectiveness of nasopharyngeal oxygen insufflation following preoxygenation using the four deep breath technique within 30 s, on the onset of haemoglobin desaturation during the subsequent apnoea. Thirty ASA I or II patients were randomly allocated to one of two groups. In the study group (n = 15), pre-oxygenation was followed by insufflation of oxygen at a flow of 5 l.min−1 via a nasopharyngeal catheter commenced at the onset of apnoea. In the control group, pre-oxygenation was not followed by nasopharyngeal oxygen insufflation (n = 15). In the control group, SpO2 fell to 95% within a mean (SD) apnoea time of 3.65 (1.15) min, whereas in the study group, SpO2 was maintained in all patients at 100% throughout the 6 min of apnoea, at which point apnoea was terminated and positive pressure ventilation commenced. We conclude that nasopharyngeal oxygen insufflation following pre-oxygenation using the four deep breath technique can delay the onset of haemoglobin desaturation for a significant period of time during the subsequent apnoea.