Abstract
Cyclophosphamide can rarely cause interstitial pneumonitis and fibrosis. Although it has been reported previously in patients being treated for lymphoma, it occurred in this case in a man under treatment for glomerulonephritis. The temporal sequence of the respiratory insufficiency and the histopathology, when compared to the previous examples in the literature, suggest that cyclophosphamide was aetiologically responsible for the lung disease. There may be an interval of one or more months after discontinuation of cyclophosphamide therapy before clinical or radiological improvement occurs.