Social survey data is essential to measuring equality, for the assessment of change over time, and to the evaluation of the impact of new policies. In this article we have identified and evaluated the statistical data and evidence on religion in the UK in relation to key policy areas, such as employment, housing, health, education, and criminal justice. For each data source, we consider definitions, data collection, coverage of issues, sample size, and data access. We examine the multi-faceted nature of religion and consider the links between religious and ethnic identities. We also outline models that can link religious identity to equality outcomes (and hence potentially allow the measurement of discrimination) and identify the evidence gaps. The UK has one of the most religiously diverse populations in the European Union, both in terms of diversity within Christianity and between different world religions. However, while religion is increasingly recognised, in both legal and policy terms, as an important equality issue, the data on the dynamics of religion in the UK are limited. The inclusion of a new question on religion in the 2001 Census in England, Scotland, and Wales is a major new source of data, but data are limited regarding the role and significance of religion in people's everyday lives, particularly among ethnic minority populations. It is clear that there is a need for a far more comprehensive and rounded approach to data on religion in the UK, which takes account of its multi-dimensional nature.