Background:Gastroesophageal reflux disease (GERD) prevalence in patients with sulfur mustard (SM)-induced bronchiolitis obliterans (BO) is higher than exposed cases with mild lung injuries. In this study, we aimed to evaluate the prevalence of microaspirations using nuclear scintiscan among BO patients with SM exposure. Methods: This was a prospective cross-sectional study conducted on patients with SM-induced BO and pulmonary symptom exacerbation referred to the Baqiyatallah Hospital, Tehran, Iran during the year 2009. Following the endoscopy-based diagnosis of GERD by a gastroenterologist, anti-reflux medications were withdrawn for 72 hours and then the patients underwent nuclear scintigraphy scan following 12 hour ingestion of fat containing food as radionuclide dinner. High resolution computed tomography (HRCT), spirometry and bronchoscopy were also performed for all patients. Results: In this study, 39 patients (94.9% men) with mean (± SD) age of 45.1 ± 6.2 years were enrolled. The most common clinical complaints of the patients were thick sputum (97.4%) and dyspepsia (94.7%), followed by chest tightness (89.7%), nocturnal cough (82.1%), and nocturnal dyspnea (66.7%). In HRCT, air-trapping was the most common pulmonary finding (92.1%). In spirometry, mean (±SD) FEV1 and FEV1/FVC were 52.7 ± 22.4% and 70.4 ± 13.9%, respectively. In bronchoscopy, the most common finding was airway remodeling (62.2%), followed by false vocal cord hypertrophy (24.3%). In scintigraphic imaging, only 1 patient had a remarkable finding, in whom, the radionuclide material was seen in the pharynx (proximal GERD), but did not produce marked microaspiration of gastric substances into the airways. Conclusion:Although previous reports demonstrated high prevalence of GERD and microaspiration in patients with SM-induced BO, we did not find remarkable evidence for microaspiration in scintiscan in patients included in this study.