Patients with gastro-oesophageal reflux disease (GORD) swallow air more frequently and have more gas-containing reflux episodes than healthy controls. One explanation for this phenomenon may be that GORD patients primarily swallow more frequently and, as a consequence, have more swallow- or transient lower oesophageal sphincter relaxation-associated reflux episodes. Another explanation may be that GORD patients swallow more often in response to perception of reflux episodes. The aim of this study was to differentiate between these two possible mechanisms. In 34 patients with typical reflux symptoms oesophageal 24-h pH-impedance monitoring was performed twice, once off and once on proton pump inhibitor (PPI) therapy. The number of reflux episodes and number of swallows and air swallows was evaluated. The symptom association probability (SAP) was used to distinguish patients with a good relationship between symptoms and reflux episodes (SAP+) from those who had not (SAP-). In both the SAP+ (n = 21) as SAP- patients (n = 13), the acid exposure time decreased during PPI therapy. In the SAP+ patients, the number of swallows decreased on PPI (829 +/- 85 off vs 701 +/- 79 on PPI, P < 0.05), whereas in the SAP- patients, the incidence of swallows (802 +/- 93 off vs 814 +/- 69 on PPI, P = NS) was not influenced by the PPI therapy. PPI therapy reduces the number of swallows in patients with a positive SAP, but not in those with a negative SAP. This finding supports the hypothesis that the increased incidence of swallows in GORD is brought about by responses to perceived reflux events.