This paper was prepared along with three companion documents to facilitate discussion during a Demographic Analysis (DA) technical review workshop. The paper focuses on Medicare enrollment as a source for estimating the population aged 65 and older on April 1, 2010. Three major issues are discussed:

• Not all United States residents aged 65 and older are enrolled in Medicare - either by law, or by preference. Correction factors need to be applied to the Medicare Enrollment Database (MEDB) to obtain an accurate estimate of the size and distribution of the United States population on April 1, 2010 by single year of age, sex, and race.
• There are records in the MEDB that should be excluded from the DA estimates. This includes people under 65 who qualify for Medicare, enrollees with residences outside of the United States, and records for people who were deceased as of April 1.
• The MEDB contains records with unknown and missing race codes. Also, Hispanic origin is recorded as a race category in the MEDB. These records need to be assigned a race code of Black or non-Black.

The paper proposes strategies for meeting the challenges associated with these issues.