Nasal obstruction influences respiration during sleep and nasal packs may cause obstructive sleep apnoea. In order to investigate this, the perioperative oxygen saturation was monitored for 3 nights with continuous pulse oximetry in 12 patients, who had bilateral nasal packs after septoplasty. A significant increase in the number of nocturnal episodes of hypoxia and a significant prolongation of the mean duration of the individual hypoxic periods were demonstrated during the first and the second post-operative nights. The clinical significance of these results is as yet unknown, but the use of partial nasal packing in septoplasty is advocated. Further investigations of nocturnal oxygen desaturation and design of nasal packs, securing the post-operative nasal airway, are needed.