In two patients with diabetes insipidus the development of an allergic alveolitis with transition into pulmonary fibrosis could be observed. The alveolitis is evoked by snuffing of posterior pituitary extracts. The pathomechanism of this side effect (disease) is similar to those of other allergic alveolitides (e.g. farmer's lung, bird-fancier's lung, malt-worker's lung etc). This disease can be avoided by changing the therapy of diabetes insipidus to fully synthetic preparations free of protein. When irreversible changes are already present at the stroma of the lung (X-ray picture, function of the lung, histology), then the therapeutic possibilities are restricted and the prognosis is unfavourable.