The possible causes of excessive swallowing of air leading to bloating, which is common in Rett syndrome (RS), were investigated during feeding and at rest. Seven individuals with RS aged between 4 and 33 years (three with air bloat) underwent feeding videoflouroscopy and concurrent respiration monitoring. The results were compared with a randomly selected group of 11 individuals, aged between 2 and 16 years, with quadriplegic cerebral palsy and feeding problems, some of whom had mild air bloat. All individuals from both groups had isolated pharyngeal swallows and several mouth breathed; this may account for some air swallowing but not the severe air bloat characteristic of RS. Thirty-three individuals with RS aged between 3 and 44 years were monitored for nasal respiration, chest movements, swallowing, and vocal cord position at rest (between feeding). Twenty had air bloat, 17 of whom swallowed air during breath-holding in the same way, and three gulped air during hyperventilation. Of the 13 without air bloat, eight did not have recurrent breath-holding and five did, but without concurrent air swallowing. Several methods for reducing air swallowing in apnoea were investigated. The most successful was a dummy with an air leak, but this was poorly tolerated and could only be used for short periods of time. Apnoeas and air bloat are often worse when individuals are distressed and may in some individuals be reduced by anxiolytic medications.