Race and ethnicity are commonly used variables in medical research. Each year about 2500 papers are indexed under the headings “ethnic groups” or “racial stocks” on Medline1; many more control for ethnic group or cultural differences during analysis. Patterns of disease, response to treatment, and the use of services are increasingly being explained in ethnic or racial terms, and from next April providers in the NHS must collect “ethnic data.”

However, substantial problems exist with this burgeoning literature. The categories of race or ethnic group are rarely defined, the use of terms is inconsistent, and people are often allocated to racial or ethnic groups, arbitrarily.2 Some researchers use the original Blumenbach classification3 and class “Asians” as “Caucasian,” though modern definitions often class “Asians” as “black.”4 Some use “Afro- Caribbean” for people of African or Caribbean descent; others use it for people who are black and of Caribbean ancestry. The King's Fund no longer uses the term “ethnic” because of its heathen connotations and classes all disadvantaged groups as “black populations,” believing that the experience of racism is paramount.4 Meanwhile, the commission for Racial Equality uses the term “ethnic minorities,” believing that cultural and religious differences are important (Commission for Racial Equality, personal communication).

Race is …