Bacteriologic evidence that cases of pneumonia following influenza might be due to B. influenzæ alone was very meager in the group of cases studied clinically at Camp Pike; in fact, no convincing evidence was obtained that such cases occurred. In one case B. influenzæ alone was found in the sputum coughed from the deeper air passages, and in another case B. influenzæ with a few colonies of S. viridans was found. Both were cases of bronchopneumonia, mild in character, and recovered promptly. They presented no clinical features by which they could be distinguished from cases of pneumococcus bronchopneumonia. It has been previously stated that B. influenzæ was found in all early uncomplicated cases of influenza somewhere in the respiratory tract; that it was present together with other organisms, notably pneumococcus in the sputum from cases of purulent bronchitis following influenza; and that it was found in the sputum coughed from the lung in approximately 80 per cent of cases of pneumonia complicating influenza. In 35 cases it was very abundant, often being the predominating organism. In all these cases, however, pneumococci or hemolytic streptococci were also present in considerable numbers at the time of onset of the pneumonia. It is impossible to say merely from the clinical and bacteriologic data under consideration what part B. influenzæ played in the development of the actual pneumonia in these cases. Discussion of this subject is therefore reserved for the section of this report dealing with the pathology and bacteriology of pneumonia following influenza. Summary Influenza as observed at Camp Pike presented itself as a highly contagious infectious disease, the principal clinical manifestations of which were, sudden onset with high fever, profound prostration with severe aching pains in the head, back and extremities, erythema of the face, neck and upper chest with injection of the conjunctivæ, and a rapidly progressive attack upon the mucous membranes of the respiratory tract as evidenced by coryza, pharyngitis, tracheitis and bronchitis with their accompanying symptoms. In the majority of cases it ran a short self-limited course, rarely of more than four days’ duration, and was never fatal in the absence of a complicating pneumonia. Bacteriologic examination in early uncomplicated cases of the disease showed the B. influenzæ of Pfeiffer to be present in all cases, often in predominating numbers. It was found more abundantly present during the acute stage of the disease than during convalescence in uncomplicated cases. No other organisms of significance were encountered by the methods employed.