This paper is a review of issues associated with measuring ethnicity and using ethnicity measures in social science research. The review is orientated towards researchers who undertake secondary analyses of large-scale multipurpose social science datasets. The paper begins with an outline of two main approaches used in social surveys to measure ethnicity, the ‘mutually exclusive category’ approach and the ‘multiple characteristics’ approach. We also describe approaches to the use of ethnicity measures in cross-national comparative research. We emphasise the value of sensitivity analyses. We also encourage researchers to carefully consider the possible relationships between ethnicity and other important variables in order to avoid spurious interpretations of the effects of ethnicity.