The aim of this study was to clarify the influence of gastroesophageal reflux (GER) on cough threshold in patients with digestive symptoms but free from respiratory involvement. Of 57 consecutive subjects referred for 24-h esophageal pH monitoring because of digestive reflux symptoms, 29 patients free from respiratory disorders were studied. They underwent esophageal pH monitoring and manometry, upper gastrointestinal endoscopy, pulmonary function tests, and methacholine and capsaicin challenges. The methacholine test was performed by inhalation of increasing doses of methacholine up to 4,000 micrograms; the results were expressed as the dose causing a 20% decrease in FEV1 from baseline (PD20). The capsaicin threshold was evaluated by inhalation of increasing doses of capsaicin from 0.3 up to 9.84 nmol, expressing the results as the dose of capsaicin eliciting five coughs (PD5). Fifteen patients were considered refluxers on the basis of a total esophageal acid exposure time above 4.7%. Esophagitis grade 0 was found in 15 patients, grade 1 in seven patients, grade 2 in seven patients. PD5 was significantly lower in refluxers (median 0.51 micrograms, range 0.22 to 19.8) than in nonrefluxers (19.8 micrograms, range 0.31 to 19.8) (p < 0.001); there was no difference in baseline ventilatory parameters and in airway responsiveness to methacholine between the two groups. All patients with a pathologic acid exposure time but one had a low cough threshold, irrespective of the presence or absence of esophagitis.(ABSTRACT TRUNCATED AT 250 WORDS)