The authors report a case of hypersensitivity lung disease due to salazosulfapyridine in a subject treated for ulcerative colitis. The diagnosis was made by a provocation test and by immunological examinations in vitro. They then analyse two identical observations already noted in the literature, then they situate this complication in the field of the already known side effects of salazosulfapyridine then in the group of lung diseases due to drug hypersensitivity. Finally, they attempt to analyse the various allergo-immunological reactions which may intervene in the onset of this lung disease. © 1979 Expansion Scientifique Française.