Universities are increasingly making decisions about undergraduate admissions with reference to contextual indicators to identify whether an applicant comes from a disadvantaged family, neighbourhood or school environment. However, the indicators used are often chosen because they are readily available, without consideration of the quality of possible alternatives. A review of existing research literature to assess potential contextual indicators yielded around 120,000 reports, and 28 categories of indicators. Each indicator was assessed on the basis of existing evidence concerning its relevance, reach, availability, accuracy, reliability and completeness. Many possible indicators are not readily available, or accurate enough for use in practice. Indicators concerning individual circumstances are generally safer than area-based or school characteristics. There are some indicators for very small categories that can be used relatively un-problematically as long as the data can be made available at time of candidate selection. None of these is a solution to the more general issue of contextualised admissions. Having a disability or special educational need is clearly linked to lower attainment and participation but not for all categories. The most suitable general indicator is eligibility for free school meals (FSM), based on the number of years an applicant has been known to be FSM-eligible.