In the city of Pittsburgh the disease was not made reportable until October 5. However, one case was reported on October 1, and it was known that there were a few isolated cases in Pittsburgh previous to that date. During the months of October, November and up to December 21 there were 23,268 cases of influenza reported, and the deaths were 1,374 from lobar pneumonia and 678 from broncho-pneumonia. We cannot but feel that most of the deaths reported during the period of the epidemic as lobar pneumonia were broncho-pneumonia associated with influenza. It was well known among civilians that true lobar pneumonia was exceedingly rare and has remained so up to the present time. This is especially noticeable, as this is the time of the year when lobar pneumonia is usually widespread in Western Pennsylvania. This district was particularly favored with a mild fall and winter. On October 1 the first case was reported, on October 15 the epidemic reached its peak—on that day 957 persons being reported ill with the disease. From October 16 until October 28 it maintained an average of 600 cases daily; from October 29 until October 31 there was a sharp decline from 600 cases daily down to 200 cases daily. From November 1 until December 21 the decline has been uniform, and on this latter date 58 cases of influenza and 7 of pneumonia were reported. The height of the epidemic was reached between October 15 and October 29. During the period of the epidemic in Pittsburgh, from October 1 until December 15, 62 days were recorded as cloudy, or partially cloudy, and only 14 days as clear, although the cloudy days seemed distributed and not in decided groups. The mean temperature for October was 58 degrees, with normal 54.9; for November, 44 degrees, normal 42.9; for December, 41 degrees, normal 34.7. The precipitation in October was 3.08, as against a normal of 2.36; in November, 1.79, with normal 2.55; and in December, 3.50, normal 2.73. From a study of these weather reports we see that the epidemic occurred during a period of abnormally warm, cloudy and slightly more moist autumnal season than usual, but these variations were relatively slight and far from decided. The confusion of diagnosis between lobar pneumonia and broncho-pneumonia, associated with or following influenza, occurred in the Pittsburgh health reports as well as in other cities. The presumption that almost all, if not all, of the cases reported as pneumonia of different types were really cases of influenzal pneumonia, seems justified. _Epidemic Incidents in Institutions and Towns of Western Pennsylvania_