['The link between organizing pneumonia (OP) and gastroesophageal reflux disease (GERD) is not well known. There is little evidence in the literature to establish a causal link between GERD and OP.', 'The aim of the study was to assess the hypothesis that OP is more severe when it is associated with GERD and that it leads to more frequent relapses.', 'In a retrospective study on 44 patients suffering from OP, we compared the clinical, radiological and histological characteristics of 2 groups, 1 composed of patients with GERD (n = 20) and the other of patients without GERD (n = 24).', 'The GERD group was distinguished by a higher number of patients with migratory alveolar opacities on chest radiography and thoracic computerized tomography (14/20 vs. 9/24; p = 0.03 and 18/20 vs. 13/24; p = 0.01), greater hypoxemia [60 (42-80) vs. 70 (51-112) mm Hg; p = 0.03], greater bronchoalveolar lavage cellularity [0.255 (0.1-1.8) vs. 0.150 (0.05-0.4) g/l; p = 0.035] and more frequent relapses (14/20 vs. 9/24; p = 0.03).'] Is gastroesophageal reflux disease a risk factor for severity of organizing pneumonia?