Loeffler reported in 1932 and again in 19361a syndrome characterized by transitory pulmonary infiltrations, blood eosinophilia and a mild clinical course which was in striking contrast to the extensive pulmonary lesions as seen in the roentgenograms. Some of the cases were discovered in supposedly normal persons in the course of mass radiography, while others were in ambulatory cases suspected of pulmonary tuberculosis. Symptoms when present were those of fatigue, irritating cough, associated sometimes with pain in the chest and with scanty sputum; normal or moderately elevated temperature; mild leukocytosis, and increased sedimentation rate. Exaggerated vesicular breathing and sibilant rales over the area of infiltration were the only auscultatory signs. The eosinophilia ranged from 6 per cent to 66 per cent and accompanied rather than followed the appearance of the infiltration of the lung, so that it could not be considered a post-infectious phenomenon. However, strict parallelism between the