This report is based upon a series of investigations carried on during the epidemic of influenza at Pittsburgh. This epidemic reached Pittsburgh about the last week of September, 1918, rapidly spreading through the community during the first days of October. Pittsburgh had been warned of its coming through the experience of Boston, where the epidemic made its appearance during the late days of August. To a certain extent the warning from the East permitted the making of preparations to control its ravages. But even with the attempt for the protection of public health the epidemic advanced with all its virulence, rapidly picking out the susceptible individuals and leading to a high death rate.