The aim of the study was to characterise gastro-oesophageal reflux (GOR) in idiopathic pulmonary fibrosis (IPF). 40 consecutive IPF patients underwent pulmonary high-resolution computed tomography (HRCT) scan and impedance-pH monitoring while off antisecretory therapy. The presence of pulmonary fibrosis was assessed using validated HRCT scores. Reflux features included distal oesophageal acid exposure, number of acid/weakly acidic reflux episodes and their proximal migration. 40 consecutive patients with interstitial lung disease other than IPF (non-IPF patients) and 50 healthy volunteers were also enrolled. IPF patients had significantly higher (p<0.01) oesophageal acid exposure (median (interquartile range (IQR)) 9.25 (4.7-15.4)% versus 3.3 (1.4-7.4)% versus 0.7 (0.2-4.2)%, number of acid (median (IQR) 45 (23-55) versus 32 (19-44) versus 18 (10-31)), weakly acidic (median (IQR) 34 (19-43) versus 21 (11-33) versus 18 (15-28)) and proximal reflux (median (IQR) 51 (26.5-65.5) versus 20 (9.5-34.5) versus 9 (5-20)) events compared to non-IPF patients and healthy volunteers, respectively. Pulmonary fibrosis HRCT scores correlated well with reflux episodes in both the distal (r(2)=0.567) and proximal (r(2)=0.6323) oesophagus. Patients with IPF had more bile acids and pepsin (p<0.03) in bronchoalveolar lavage fluid (BALF) (62% and 67%, respectively) and saliva (61% and 68%, respectively) than non-IPF patients (25% and 25% in BALF, and 33% and 36%, respectively, in saliva) and controls (0% and 0% in BALF and saliva, respectively). Acid GOR is common in IPF, but weakly acidic GOR may also occur. Patients with IPF had a risk of pulmonary aspiration of gastric contents. Outcome studies with intense antireflux therapy are needed.