The epidemic of influenza, prevalent in Europe during the Great War, was watched with interest everywhere, not only because of its military importance, but also because of the danger of its spreading to other continents. The prediction that this would occur, made months before its realization, was verified on an even larger scale than had been anticipated, for in the autumn of 1918, this acute respiratory infection passed over the United States like a huge wave, taking a tremendous toll in human lives; later smaller waves followed leaving in their wake corresponding degrees of devastation. The first cases of the disease appeared on the New England coast, and New Haven was among the cities to be early invaded, though here the epidemic was somewhat less severe than in other cities along the Atlantic Seaboard. Forewarned and alert to the danger, medical men spared no effort in studying the disease; as a result, no malady, perhaps, has ever been investigated so intensively and from so many different points of attack in an equal length of time. Proof of this appears in the abundant literature issuing from every quarter. Among the various contributions to this subject, many include the anatomical changes associated with the disease. In general, however, these are brief; and although they serve their special purpose well, they have not been elaborated sufficiently to close the chapter. During a period of about three months beginning with September 18, 1918, while the epidemic raged and waned in New Haven, there were approximately eleven hundred cases of the disease admitted to the New Haven Hospital. As is so often true, only the more critically ill sought hospital care, and few, if any, patients affected by other respiratory infections are included in these statistics. The mortality here, as elsewhere, was very high; of two hundred eighty (280) cases that ended fatally, eighty-two (82) were investigated at the post-mortem table. An attempt was made to make the studies very complete, and this was favored since the headquarters of the Yale Army Laboratory School, under the command of Colonel Charles F. Craig, were located at the Brady Laboratory where a large number of men were being instructed in Pathology and Bacteriology. It was also fortunate that competent illustrators were available who made a splendid series of water-colors and drawings of the characteristic lesions, both gross and microscopic. The number of autopsied cases at the New Haven Hospital was augmented by a series of acute fatalities from the same disease at the United States General Hospital No. 16, at Allingtown, West Haven, where the anatomical studies were carried on by the same group of men. The latter autopsies offered nothing new, but served to corroborate the conclusions reached at the New Haven Hospital.