The National Office of Vital Statistics, U. S. Public Health Service, Federar Security Agency, Washington, D. C, has just released a summary on infant mortality in the United States for 1945. The record of progress is impressive. From 99.9 deaths per thousand live births for the birth registration states in 1915, the infant mortality has decreased almost continuously to 38.3 in 1945. However, the reduction was not shared equally by each of the age groups. The rates of decline vary inversely with age. The largest decreases occurred for infants over 1 month of age, the rate for the 6 to 11 months age group having dropped 80 per cent and that for the 1 to 5 months age group 71 per cent since 1915. The corresponding relative decreases for the age groups under 1 month and under 1 day were 45 per cent and 25 per cent, respectively. These differences in the rate of decrease for each age group have been accompanied by an increase in the importance which mortality during the earliest days of life bears to total infant mortality. Neonatal mortality (i. e., mortality under 1 month of age) constituted a decidedly greater proportion of total infant deaths in 1945 than in 1915.