Early diagnosis of interstitial fibrosis

2 cases of interstitial fibrosis of the Hamman-Rich type are presented. The patients were symptomatic, but had normal X-rays. They were suspected of having interstitial infiltration by pulmonary function tests. Diagnosis was confirmed by lung biopsy. Pulmonary function tests, especially the study of elastic properties of the lung, can be of primary help in the diagnosis of pulmonary interstitial infiltration and fibrosis when the patient's X-ray is normal.