Interstitial pneumonitis in children is a rare and poorly understood disease. Controversy exists as to whether the varoius histologic changes encountered represent different disease or a spectrum of the same disease. Fourteen biopsy-confirmed cases of desquamative interstitial pneumonitis in children were seen at the Mayo Clinic between 1953 and 1975. A search of the literature revealed 14 additional cases but no series of exclusively desquamative interstitial pneumonitis. The most frequent symptoms were retardation of growth and dyspnea, often accompanied by cough. Tachypnea was the most common finding on examination; rales, cyanosis, and clubbing were variably present. The chest roentgenogram was distinctly abnormal in all cases; it usually revealed a combined interstitial and alveolar pattern extending bilaterally from the hilus to the base. Results of laboratory studies were nonspecific for desquamative interstitial pneumonitis. All 28 patients in this review were treated with corticosteroids; 17 (61 percent) survived. Desquamative interstitial pneumonitis was found in association with a variety of other major illnesses. The cause remains unknown.