SummaryA patient is described who developed a pulmonary hypersensiiivity reaction to sulphasalatzine used in the treatment of his ulcerative colitis. Challenge testing demonstrated that the patient was sensitive to the sulphapyridine component of the drug. The pulmonary response consisted of an immediate bronchial obstructive reaction and a late parenchymal reaction with fall in gas transfer factor. Detailed immunological testing failed to define the mechanisms of drug toxicity.