Once again, Frost gives the most comprehensive discussion of the subject. He found, as we have stated, that the influenza case incidence in persons over fifteen years of age was higher in females than in males, and that in persons under fifteen the relative incidence as between males and females is variable, but with very slight excess in males for the localities studied, combined. On the other hand, the case fatality, the per cent. of influenza cases dying, under fifteen years of age, was higher in females than in males. Over sixty years of age it was considerably higher among the females, but between the ages of fifteen and sixty the general tendency was to a much higher case fatality among the males. The difference was greatest between the ages of 20 and 40. The case fatality between the ages of 15 and 45 in the group of southern and central states was in decided contrast to that in the Northern Atlantic and Pacific groups, the case fatality in the former being remarkably low in both sections and slightly higher in females than in males. He suggests that in the south and middle west where the epidemic was generally milder in respect to mortality than in the northeast and far west, the essential difference was not in case incidence, but in case fatality, especially in persons from 15 to 45 years of age, and in the relatively low case fatality among young male adults. Frost makes the important point that the relative mortality is determined more accurately by case fatality than by case incidence, and that without a full and exact knowledge of the variations in case fatality, statistics of mortality are by no means translatable to terms of relative morbidity. The fact that certain cities showed, as described by Pearl, relatively high mortality rates, does not give conclusive evidence that the morbidity was higher in these cities than elsewhere. The lower influenza case fatality in females from 15 to 60 years of age appears to be accounted for in part at least: first, by a decreased incidence of pneumonia as compared with the males; and, second, by a lower fatality in those cases which did develop pneumonia. The relatively small number of fatalities in our own records do not warrant a classification by age groups. We found that for all ages in 1918 7.9 per cent. of females developed pneumonia as contrasted with 6.8 per cent. males. This does not include those who died. In 1920, 1.87 per cent. of the male cases died, while only 0.37 per cent. of the females died. Five and fifteen-hundredths per cent. of all male cases developed pneumonia and recovered, and 3.56 of the females did likewise. In 1920 a higher proportion of males than females developed pneumonia, and likewise a higher proportion died.