The hypothesis that suppression of transient lower oesophageal sphincter relaxation (TLOSR) in recumbent postures in the dog is dependent upon the sensing of a gastric pool of liquid in proximity to the lower oesophageal sphincter was examined. Constant gastric insufflation with air (80 ml/min) was used to evoke TLOSR in unsedated, fasting animals. Oesophageal motility was monitored with a perfused manometric sleeve catheter assembly. Gastrooesophageal flow was recognized manometrically and by oesophageal pH recording. TLOSR occurred significantly less frequently in three recumbent positions (right lateral, left lateral and supine) than when the dog stood on four legs, but was more likely to be associated with acid reflux when they occurred in recumbent positions. Aspiration of the gastric pool was found to have no effect on triggering of TLOSR although it reduced the frequency with which acid reflux was associated with TLOSR. It is concluded that the low rate of occurrence of TLOSR in recumbent positions is unlikely to be explained by the presence of a gastric pool of liquid in proximity to the lower oesophageal sphincter.