Cities exist in a world of cities and thus routinely invite a comparative gesture in urban theorizing. However, for some decades urban studies have analytically divided the world of cities into, for example, wealthier and poorer, capitalist and socialist, or into different regional groupings of cities, with subsequently very little comparative research across these divides. Interest in drawing comparisons among different cities has escalated in an era of ‘globalization’, as economic and social activities as well as governance structures link cities together through spatially extensive flows of various kinds and intense networks of communication. Nonetheless, scholars of urban studies have been relatively reluctant to pursue the potential for international comparative research that stands at the heart of the field. Where an interest in globalization has drawn authors to explicit exercises in comparison, both the methodological resources and the prevalent intellectual and theoretical landscape have tended to limit and even undermine these initiatives. This article seeks, first, to understand why it is that in an intrinsically comparative field with an urgent contemporary need for thinking across different urban experiences, there has been relatively little comparative research, especially comparisons that stretch across the global North–South divide, or across contexts of wealthier and poorer cities. Secondly, through a review of existing strategies for comparing cities, the article considers the potential for comparative methodologies to overcome their limitations to meet growing demands for international and properly post-colonial urban studies. Finally, it proposes a new phase of comparative urban research that is experimental, but with theoretically rigorous foundations.