Over the past decade there has been much discussion of the challenges posed by rapid urbanization in the developing world; yet the health of the urban poor, and especially those residing in low- and middle-income countries, continues to receive little political priority in most developing countries and at the global level. This research applies social science scholarship and a public policy analytical framework to assess the factors that have challenged efforts to make health in urban poor settings a priority. We conducted 19 semi-structured phone interviews with key urban health proponents and experts representing agencies that shape opinions and manage resources in global health. We also conducted a literature review, which included published scholarly literature and reports from organizations involved in urban health provision and advocacy. Utilizing a process-tracing method, we triangulated among these sources of data to create a historical narrative and analyse the factors that shape the global level of attention to and resources for urban health. The urban health agenda continues to be challenged by six factors, three of which concern the political context or characteristics of the issue: long-standing competition with the dominant development agenda that is rural health oriented; limited data and measurement tools that can effectively gauge the extent of the problem; and lack of evidence on how to best to address the issue. The other three factors are directly under the control of the urban health community: the community's ineffective governance; little common understanding among its members of the problem and how to address it; and an unconvincing framing of the issue to the public. The study offers suggestions as to what advocates can do to secure greater attention and resources in order to help address the health needs of the urban poor.