This article analyses and contrasts the growth and development of regionalism in Africa and the Middle East and considers what lessons can be drawn from these regions for studies of the European Union. Rather than asking why regionalism has failed in certain parts of the world, while succeeding in Europe, it takes a more nuanced view of the processes associated with regionalism, regionalization and regional integration. It identifies the particular conditions which have led to the rise of regional organizations in Africa and the Middle East and then singles out four factors of importance in understanding the relative success or failure of different schemes, namely external influence; hegemony and leadership; regime type and identity. This discussion then forms the backdrop to a comparative consideration of the European Union. In highlighting those factors which account for the different trajectories of regional institutions, the article aims to widen the scope of EU and comparative regionalism studies.