Assistance from the laboratory was meager, especially in the early days of the epidemic. This was due largely to the inability to get laboratory workers in sufficient numbers to follow the work through, but more largely to the fact that we were unable to interpret the unusual laboratory results which were available. When we were once fully aware of the difficulties in diagnosis which confronted us, we utilized every practical means at our disposal. Among these was an examination of the chest with the X-ray. On account of lack of facilities and of help, it was impossible to make routine X-ray examinations of the chest in all cases. Besides, it was difficult to interpret the X-ray findings, on account of the unusual character of the lesions. Also, many of the patients were so desperately ill one hesitated to disturb them. We hear that other clinics had similar experiences, and that very little substantial help came from the X-ray, except in cases with complications. Several attempts were made to determine the kind of shadow, if any, the “cyanotic, œdematous, wet” lung would make, but no satisfactory observations have been forthcoming. From our own observations and from the discussions of other observers, it would seem to us that the stereoscopic examination of these chests is the only possible way of getting satisfactory plate readings in these cases where the pathology seems so lawless in its extent and peculiar in its distribution. This method of examination, however, demands facilities convenient at the bedside and perfect co-operation of the patient—difficult conditions to meet under the circumstances. In the acute cases, when the desire to make a diagnosis not only of the presence but of the extent of the disease was keen, X-ray examination was largely impractical. In cases of delayed resolution, or in cases with complications with prolonged convalescence, X-ray examinations were extremely helpful. _Diagnosis of Influenzal Pneumonia_ In the consideration of any disease the well-trodden path of a painstaking history, a thorough physical examination, and reliable laboratory investigation, together with an intelligent interpretation, will usually lead to a definite diagnosis. In certain diseases, as is well known, the stress must be placed about equally on all of these factors, while in others one or other factor predominates. In influenzal pneumonia, until more is known of the etiology (bacteriology) and of the pathological changes and of the physiological disturbances, the controlling factor in the diagnosis (we feel embarrassed to admit) must be the history. This is true not only of the diagnosis of influenza with or without pulmonary involvement, but is also true of the diagnosis of the various complications, and will be found to be particularly true in the recognition of the bizarre sequelæ, which no doubt in the succeeding months or years will be attributed to or will follow in the train of influenza.