This study was designed to investigate the incidence of critical events in breathing following light general anaesthesia compared with normal sleep during the first 12 h after transfer from the recovery room. There were no significant differences in the incidence of apnoea or desaturation episodes between normal sleep and the post-operative recovery period. There was a close correlation between the pre-operative and post-operative incidence of apnoea (r = 0.93), pre-operative and post-operative desaturation periods (r = 0.81), pre-operative and post-operative mean SpO2 values (r = 0.54) and pre-operative and post-operative minimal SpO2 values (r = 0.90) in all the patients. In the early post operative period, breathing patterns and oxygenation were similar to those observed during normal night-time sleep in elderly patients under going ophthalmological surgery.