Thirty-six patients with bilateral symmetrical presbyacusis who reported a temporary improvement in the hearing of one ear following a Valsalva's manoeuvre were further investigated. Bone conduction and air conduction thresholds, middle ear pressure and middle ear compliance were measured before and after Valsalva's manoeuvre in the ears which had a subjective improvement in hearing following auto-inflation. Bone conduction thresholds remained unaltered in 66 per cent of ears while average air conduction thresholds varied by less than 5 decibels. Middle ear pressure was unchanged in over half the ears tested and in 81 per cent of the ears there was no change in middle ear compliance. There appears to be no simple explanation for the temporary subjective fluctuation in hearing reported by patients with presbyacusis.