The recorded death rate from leukemia in the United States has risen continuously since 1900, with an accelerated rate of increase since 1930. The rise from a rate of 1.9 per 100,000 population in 1920 to 3.7 in 1940 represents an increase of 94.7 per cent in this twenty-year period. This increase cannot be accounted for by changes in the age distribution of the population, for the age specific death rates have increased in each age group. The factor of increasing recognition of the disease resulting from improved diagnostic technics and greater use of hospitals with their laboratory facilities must be given adequate consideration in an effort to determine the causes for the rising death rate. White persons are affected at a rate more than twice as great as nonwhites. Some of the difference must be attributed to variations in the availability of diagnostic services. Males experience a rate approximately one-third greater than females. Leukemia affects persons in the older ages, particularly over 55 years, with the greatest frequency, and the population under 5 years of age experiences a mortality rate higher than any other age under 45 years. In the intermediate ages the death rate falls to the lowest point. In 1940 the death rate from leukemia for all ages was 3.7 per 100,000 population. The highest rate, 15.7 per 100,000 occurred in the age group 75-84 years. Under 1 year the rate was 4.9 per 100,000. The lowest rate, 1.5 per 100,000, occurred in the ages from 15 to 2.4 years. Figures for the city of Baltimore for the five-year period 1939-1943 indicate an almost equal incidence of lymphoid and myeloid leukemia. Nearly two-thirds of the deaths studied in Baltimore were reported as acute leukemia. Acute myeloid leukemia appears to be more common than acute lymphoid. After age 45 chronic leukemia is more frequently observed; younger persons experience acute leukemia most commonly. Undoubtedly many deaths result from leukemia in which this disease was neither diagnosed nor recorded on a death certificate. Clinical evidence indicates that the causes in which this failure would occur most commonly are cancer, anemia, and diseases of the spleen. Statistical evidence reveals that these conditions are certified jointly with leukemia in a significant number and proportion of cases. Comparison of the experience of several countries indicates that the general trends of mortality from leukemia in the United States are common to the other communities. The death rates per 100,000 population in 1931 adjusted for differences in age and sex composition of the population were: United States, 3.5; England and Wales, 3.0; Paris 2.5; and Canada 2.3. Each year since 1940 more than 5,000 persons in the United States have died from leukemia.