A comparative analysis of how access and equity are defined and how policies have evolved reveals a number of commonalities and differences between countries. The overall trend is a movement from the priority given to "inherited merit" in the admission process through a commitment to formal equality, towards the application of some modes of affirmative action for selected under-represented groups. This overall convergence, which is accompanied by a growing appreciation of the complexity of social identities, is complemented by significant national specificity in respect of the social categories which are used to define social diversity. In the absence of appropriate comparative measures of participation, a Higher Education Participation Index is developed to facilitate cross-country comparisons. A review of current attempts to measure equity in access to higher education points to the need to develop a programme of comparative research which focuses on the social characteristics of students who are currently enrolled in higher education.