Birnbaum's 1982 study of diversity in higher education is reviewed, and the development of an indicator series on institutional diversity is evaluated. Birnbaum studied diversity in higher education in the framework of a natural selection or population ecology model, which emphasizes the importance of environmental factors in shaping populations of organizations. Organizations are viewed as evolving through three stages: variation, selection, and retention. Earlier reports have cited six dimensions of diversity: governance, output, finance, program, clientele, and delivery system. In the context of the population ecology model, the dimensions of program, clientele, and delivery system show the most promise for compatibility. Attention is directed to the following factors that have been addressed in consideration of diversity in higher education: internal and external diversity, programmatic diversity, procedural diversity, systemic or structural diversity, constituential diversity, reputational diversity, and value and climate diversity. The method and findings of Birnbaum's study are discussed, and attention is directed to how further study of diversity can build on Birnbaum's work. It is suggested that further refinement of diversity measures is not the best direction. A 12-item list of references concludes the document. (SW)