Using an end-tidal fractional oxygen concentration of 0.9 as an end point for pre-oxygenation, we have compared the time taken to achieve this end point and the safe duration of apnoea after induction of anaesthesia following pre-oxygenation in elderly patients and young adults. The times taken to reach the end point of pre-oxygenation and for the oxygen saturation to decrease to 92% during a period of apnoea were found not to be significantly different between the two age groups. It is concluded that in spite of the physiological changes that occur with age, end-tidal oxygen concentration monitoring is as useful in the elderly population as in young adults as an end point for pre-oxygenation.