This paper explores the relationship between the diversity within a higher education system and five key factors, namely: the environment, policy intervention, funding, competition and co-operation, and ranking. The exploration is based on the extent to which higher education systems, particularly those of Australia and New Zealand, have accommodated distinctive forms of higher education institutions characterised by the older traditional university at one extreme, and the newer university of technology at the other. Twelve interdependent propositions on diversity are proposed and discussed. These propositions indicate the ways in which each of the five key factors may influence institutional diversity or convergence. In the majority of circumstances, the convergent tendencies of institutions will predominate unless very specific environmental and economic conditions prevail, and/or specific directed policy is implemented.