The presence of acid in the oesophagus has been shown to stimulate salivary secretion, but the relevance of this oesophago-salivary reflex for acid clearance in physiological and pathological gastro-oesophageal reflux (GOR) is unknown. This study was designed to investigate the interrelation between oesophageal acid and both resting and stimulated salivary secretion. In 10 healthy volunteers, the acid clearance times after bolus infusion of 20 ml of 0.1 N hydrochloric acid were measured by means of ambulatory oesophageal pH monitoring. With a constant swallowing rate and resting salivary flow, the acid clearance time was significantly longer with dry as opposed to wet swallows (12.6 +/- 2.6 vs. 6.9 +/- 1.9 min; p = 0.01). When the salivary flow was doubled by chewing a gum base (26.0 +/- 3.4 vs. 13.2 +/- 2.0 ml/15 min; p = 0.005), the acid clearance time was markedly shortened (6.9 +/- 1.9 vs. 2.3 +/- 0.2 min; p = 0.02). As compared with water control, salivary flow, pH, and protein content were not affected by a bolus infusion of hydrochloric acid. This was true both for resting and gum-stimulated salivary secretion. Our study suggests that an oesophago-salivary reflex becomes effective only in prolonged episodes of GOR. This may explain why the water brash phenomenon is not regularly experienced by all reflux patients. Our study also suggests that chewing gum might be a non-pharmacological treatment option for some patients with symptomatic GOR.