Data for this article, as in previous reports, are drawn principally from the Monthly Vital Statistics Report, published by the National Center for Health Statistics. The international data come from the Demographic Yearbook and the quarterly Population and Vital Statistics Report, both published by the Statistical Office of the United Nations, which has also been kind enough to provide more recent data. Except for mortality data by cause and age, which are based on a 10% sample, all the US data for 1981 are estimates by place of occurrence based upon a count of certificates received in state offices between two dates, one month apart, regardless of when the event occurred. Experience has shown that for the country as a whole the estimate is very close to the subsequent final figures. There are, however, considerable variations in a few of the states, particularly in comparing data by place of occurrence with data by place of residence. State information should be interpreted cautiously.