Eight patients are reported whose lungs showed desquamation and/or fibrosis of unknown etiology. The similarity of certain histologic features suggests that D.I.P. (Desquamative Interstitial Pneumonia) might evolve either into an intermediate case of desquamation and fibrosis or into true chronic D.I.P.F. (Diffuse Interstitial Pulmonary Fibrosis). A pattern of subpleural reticular densities in an elderly asymptomatic patient is quite characteristic of chronic D.I.P.F. Adequate histologic material is essential, preferably through an open thoracotomy. The response to corticosteroid therapy is unpredictable in all 3 forms of the disease, but should logically be better if the disease is still in its active stage.