Efforts to increase access for and participation of groups that are underrepresented in postsecondary education (PSE) have included encouraging members of underrepresented groups to apply to PSE programmes, revising admission requirements to reduce barriers to attendance, providing assistance in completing applications for admission, and providing financial assistance. Such initiatives address different assumed causes of underrepresentation, but these assumptions are often not explicit. Drawing from programme evaluation, we describe and illustrate the use of change models to make explicit each access initiative's assumptions about barriers to participation, thus providing the basis for evaluation of the initiatives. The evaluation of an access initiative involving a change in admission requirements for an initial teacher education programme is discussed as an illustration of this approach.