Despite earlier failed attempts to establish similar regional arrangements, why were the Asia-Pacific Economic Cooperation (APEC) and the ASEAN+3 (APT) successfully created in the late 1980s and the late 1990s, respectively? Why did they take the institutional forms that they took, and why did they evolve in the way they did?

To analyze the formation of these regional arrangements, this dissertation proposes an institutionalist framework that addresses two related but analytically distinct questions: why are regional institutions created, and how are they created? Accordingly, the first stage of analysis explores the variation of state preferences concerning regionalism among key governments. It reveals that intraregional developments, such as a rise of regional economic interdependence or the development of regionalist ideas, did not quickly alter the configuration of state preferences in favor of a regionalist approach. Rather, it argues that the urgent governmental demand for both APEC and the APT was primarily driven by the defensive motive to respond to extraregional challenges.

The second stage of analysis investigates the actual political processes by exploring who played a leadership role. It suggests that at critical junctures precipitated by crises, non-great powers can exercise entrepreneurial leadership in proposing a new regionalist initiative. Both stages highlight the trigger mechanisms for inducing an urgent governmental demand for a regional mechanism and for generating political opportunities for non-great powers to take on a new initiative. In short, this dissertation concludes that the creation of both APEC and APT can be explained by three factors: a set of extraregional developments as triggers for institutional creation; the governmental demand for a regionalist project; and the supply of political leadership by non-great powers.

To analyze the institutional forms and evolution of APEC and APT, this dissertation investigates the four dimensions of institutions: membership, organizational structure, external orientation, and issue areas. The dissertation suggests that the institutional designs of both institutions reflect the common denominators of not only large states, but also small ones. More specifically, the organizational structure of both institutions was strongly shaped by the institutional preferences of ASEAN members.