This report discusses the rationale for and implications of the implementation of a new population standard for the age standardization (age adjustment) of death rates. The new standard is based on the year 2000 population and beginning with data year 1999, will replace the existing standard based on the 1940 population. This report also includes a technical discussion of direct and indirect standardization and statistical variability in age-adjusted death rates. Currently, at least three different standards are used among Department of Health and Human Services agencies. Implementation of the year 2000 standard will reduce confusion among data users and the burden on State and local agencies. Use of the year 2000 standard will also result in age-adjusted death rates that are substantially larger than those based on the 1940 standard. Further, the new standard will affect trends in age-adjusted death rates for certain causes of death and will narrow race differentials in age-adjusted death rates. Although age standardization is an important and useful tool, it has some limitations. As a result the examination of age-adjusted death rates should be the beginning of an analysis strategy.