“Sanitary conditions do not seem to have had any influence in determining the occurrence of influenza, and what share they have had in determining its extent or fatality cannot yet be decided. On the occasion of the last great epidemic, Dr. Peacock concluded, ‘The more common predisponents to disease, _e.g._, defective drainage, want of cleanliness, overcrowding, impure air, deficient clothing, innutritious or too scanty food, powerfully conduce to the prevalence and fatality of influenza.’ And Dr. Farr showed that in the last six weeks of 1847, while in the least unhealthy districts of London the annual rate of mortality was raised from a mean rate of twenty per 1,000 to thirty-eight, in the unhealthiest districts it was raised from a mean rate of twenty-seven to sixty-one. “That overcrowding and impure air must have a powerful influence in aiding the development of the epidemic follows from what we have seen of its greater prevalence among persons associated together in a confined space; and though rich and poor have alike been sufferers from the epidemic, and even royal personages have been fatally attacked by it, it cannot be doubted that poverty must have in many cases conduced to a fatal issue in persons, who, if placed under more favorable circumstances, might have recovered, seeing that it often involves not only inferior conditions of lodgment, but also want of appropriate food, of sufficient warmth and clothing, and of ability to take the needed rest.” _Distribution of the disease through the household._—During the autumn and winter epidemic of 1918 there was considerable discussion, and particularly were there popular newspaper reports of entire families being taken ill with influenza, sometimes all on the same day. This was less true of 1920. But few of us are personally acquainted with such instances and at best they must have been relatively rare. Among 1,236 families with influenza in either epidemic we found only 94 or 7.6 per cent. in which the entire family contracted the disease. No family consisting of over seven individuals was reported as having all the members of the family sick in either epidemic. Over two-thirds of the families with even numbers of individuals (464 out of 605) suffered the illness of less than half of the household. One quarter of all families of more than one (539 out of 2,107) had but one case per family. Over a third of all families of over two individuals (745 out of 2,006) had two or less cases per household. _As a rule there were at least one and usually several individuals in each household who did not contract influenza._