Desquamative interstitial pneumonia was 1st described as a distinct entity 2 years ago. It has a much better prognosis than the usual type of interstitial pneumonitis and often an excellent response is obtained with corticosteroid therapy. A patient was presented in whom the diagnosis was established by lung biopsy 6 years after the onset of dyspnea which was his only symptom. He had been observed for 3 years for possible berylliosis or pneumoconiosis. Physical findings were limited to crackling rales heard over both bases. The chest roentgenogram showed a fine infiltration radiating from both hili to the bases. Deterioration over a period of time was demonstrated by sequential function studies. The clinical and pathologic features of the disease were briefly reviewed and the 1st electron microscopic observations in this disease were described.