respondents to report more than one category of racial and ethnic background. Many federal agencies, including the National Cancer Institute (NCI), are attempting to address these challenges to identify populations accurately and trace any possible risk factors affecting their health.

Robert Hahn of the Centers for Disease Control and Prevention (CDC) points out the varying and conflicting definitions of race and ethnicity used by federal agencies, and noted the difficulty this situation creates for comparing populations. He notes four assumptions that must be confronted and redressed to operationalize such an effort (Hahn, 1992). These four assumptions have allowed for an ambiguity about terms that define or characterize racial and ethnic groups. Too often, he argues, it is assumed that:

1.	Government agencies have no conflicting classifications of denominator for disease rates, that classifications do not vary by region, sub-group, or individual, and do not change over time;
2.	Racial and ethnic categories are understood by the populations questioned and that understanding does not vary by region, sub-group, or individual;
3.	Survey enumeration, participation, and response rates are high and similar for all racial and ethnic populations;
4.	Individual responses to questions of racial and ethnic identity are consistent in different surveys and at different times.

These assumptions lead to inaccurate data by miscounting or misunderstanding both the base population denominator and the numerator(Scrimshaw and McMiller, 1996).

Anthropologists and other social scientists view "race" and "ethnicity" differently from the federal definitions of population groups noted above. In fact, the federal definitions as currently applied mix and confuse the concepts of race and ethnicity, thereby reinforcing the outmoded concept of race, failing to allow the important concept of ethnicity to be fully functional, and failing to acknowledge recent advances in our understanding of the role that genetics plays in illness and susceptibility to illness. Ethnicity is a recent term that involves how one sees oneself and how one is "seen by others as part of a group on the basis of presumed ancestry and sharing a common destiny with others on the basis of this background" (Zenner, 1996, p. 393). Common threads that may tie one to an ethnic group include skin color, religion, language, customs, ancestry, and occupational or regional features. In addition, persons belonging to the same