The cause of idiopathic pulmonary fibrosis (IPF) is unknown. The pathology suggests that IPF results from serial lung injury. It has been suggested that gastroesophageal reflux disease (GERD) may relate to the cause or the progression of the disease. The aims of this study were to determine the prevalence of GERD, the clinical presentation of GERD, and the manometric and reflux profiles in patients with end-stage IPF. Between July 2003 and October 2004, 18 patients with IPF on the lung transplant waiting list were referred for evaluation to the Swallowing Center of the University of California San Francisco. On the basis of the results of the pH monitoring test (5 and 20 cm above the lower esophageal sphincter), the patients were divided into two groups: group A, 12 patients (66%), GERD+; group B, 6 patients (34%), GERD-. The incidence of heartburn and regurgitation was similar between GERD+ and GERD- patients; reflux was clinically silent in one third of GERD+ patients. Reflux was associated with a hypotensive lower esophageal sphincter and abnormal esophageal peristalsis, and it was present in the upright and supine position. The reflux often extended into the proximal esophagus. These results show the following: (1) Two thirds of patients with IPF had GERD; (2) symptoms could not distinguish between those with and without GERD; (3) reflux occurred in the presence of a hypotensive lower esophageal sphincter and abnormal esophageal peristalsis; and (4) reflux occurred in the upright and supine positions, and often extended into the proximal esophagus. We conclude that patients with IPF should be screened for GERD, and if GERD is present, a fundoplication should be performed before or shortly after lung transplantation.