When the sexes were compared in different age groups, the female was found to be higher than the male in each age period except under 5, 10 to 14, 40 to 44, and 70 to 74. The excess of incidence in males in these groups is relatively small, and is hardly significant in the highest age groups, where the rates are computed from small figures. Frost found the most striking excess of incidence in females occurring between the ages of fifteen and forty, the difference between the sexes being relatively slight in age periods above and below these limits. Females over the age of fifteen and especially between the ages of 15 and 45 were either more susceptible to infection, or more generally and more intimately exposed than males of corresponding age. Our own records by the different age groups were remarkably similar. We have found an excess among the females in every age except under five years, 10 to 14, 50 to 54, and 60 to 64. In 1920 we found a slight excess among the males up to the age of 15, and again at the ages 55 to 65. Females predominated in all other ages (Chart XVII). Among those individuals who had attacks of influenza during both epidemics females again predominated except in the ages under 5 years, 10 to 14 and 55 to 59. In our own results we find that ages above 65 show a predominance of females. After considering both series of results it is safe to generalize in saying that above the age of 15 the female sex tends to acquire the disease in slightly greater proportion than the male sex. Chart XV shows the predominance of the female incidence in both epidemics. CHART XVII. [Illustration: Influenza 1918–19 Case Rate per 100 persons by age periods Influenza 1920 Case Rate per 100 persons by age periods Influenza 1918–19 Case Rate per 100 persons by sex and age Influenza 1920 Case Rate per 100 persons by sex and age] CHART XVIII. [Illustration: Distribution of 1918–19 cases according to severity Distribution of 1920 cases according to severity Changes in 1920 severity distribution as compared with 1918 [both sexes]] CHART XIX. [Illustration: District 1 Influenza 1918–19 Case Rate per 100 persons by age periods District 2 Influenza 1918–19 Case Rate per 100 persons by age periods District 3 Influenza 1918–19 Case Rate per 100 persons by age periods] [Illustration: District 4 Influenza 1918–19 Case Rate per 100 persons by age periods District 5 Influenza 1918–19 Case Rate per 100 persons by age periods District 6 Influenza 1918–19 Case Rate per 100 persons by age periods] CHART XX. [Illustration: District 1 Influenza 1918–19 Case Rate per 100 persons by sex and age District 2 Influenza 1918–19 Case Rate per 100 persons by sex and age District 3 Influenza 1918–19 Case Rate per 100 persons by sex and age]