This report deals with influenza and pneumonia mortality in the 50 cities with 100,000 or more population in 1910. For 35 of these cities, with an aggregate population of nearly 25,000,000, deaths from influenza and pneumonia are available by weeks from September, 1918, to date of writing. Deaths for the country as a whole are not available by weeks, so that these data for this large group of cities has considerable significance. To supplement them, monthly influenza and pneumonia death rates have been computed for the same cities for 1910-1918. Since 1915 there have occurred 10 distinct periods, each 8-13 wk. in duration, in which the mortality from influenza and pneumonia in this group of widely dispersed cities was so greatly increased as to denote epidemic conditions. Minor epidemics prior to the 1918 pandemic occurred in January, 1916, January, 1917, and April, 1918, with & very slight rise in mortality in April, 1915, also. We are accustomed to think of the epidemic of 1918 as occurring in the fall, and it is true that the enormous peak, at mid-October, overshadowed all prior and subsequent epidemics. In addition to this tremendous peak, the epidemic stretched over a period of 31 wk., from September 15, 1918, to April 19, 1919, and as late as the latter part of January, 1919, mortality from influenza and pneumonia in excess of the expected rates at that season was greater than the excess mortality during the epidemic of 1929. In the early months of 1920, a very sharp epidemic occurred, with excess mortality greater than during any other epidemic since the 1918 pandemic. In February, 1922, February, 1923, March, 1926, and January, 1929, other epidemics occurred, and in May of 1928 there was a slight rise in influenza mortality extending to many sections of the country. The combined excess mortality from influenza and pneumonia during these 6 epidemics that have occurred since the pandemic of 1918 was somewhere near 1/2 that of 1918-1919. In addition to data for these cities, this report contains monthly excess death rates for each of the 50 cities for 1910-1929 and weekly excess death rates for a large number of the cities during the 3 major epidemics, 1918-1919, 1920 and 1928-1929. In all of the epidemics, there is a great variation in severity in different cities. Moreover, there are periods of excess mortality from influenza and pneumonia in certain cities and sections of the country, which are not of sufficient importance to show in the combined data for the country as a whole. The report is intended as a rather detailed history of influenza and pneumonia mortality during 20 yrs., as a background for consideration of the situation with respect to the respiratory diseases at date of writing.