Recent years have witnessed the growth of an interdisciplinary literature that seeks to identify the indicators, measures, and processes of social and ecological resilience. In ecology, resilience refers to "the capacity of a system to absorb disturbance and reorganize and yet persist in a similar state" (Gunderson, et al. 2006). In Holling's (1973) original and influential thesis, ecological resilience is akin to "stability behavior" and refers to an ecosystem's return to equilibrium after a disturbance. Since the 1980s, scholars have applied the concept of resilience to human systems to explain how both humans and urban ecosystems respond to traumatic events, and what factors explain the pace, trajectory, and nature of recovery (for an overview, see Brand and Jax 2007). An integrative component of ecological systems and human systems, practiced by the Resilience Alliance through their journal Ecology and Society, suggests that "adaptive capacity" is an essential characteristic of resilient urban ecosystems (Dietz et al. 2003). In this conception, resilience does not just mean adjustment, recovery, and return to a pre-disturbance state. Rather, resilience implies the capacity for renewal, regeneration, and re-organization when faced with disturbances (Folke 2006; Berkes et al. 2003, 13; Olsson et al. 2004). Resilient systems are those that are able to adapt to uncertainty and surprise, absorb recurrent disturbances to retain essential structures and processes, and build capacity for learning, improve-ment, and advancement over pre-disturbance conditions (Adger, et al. 2005; Folke 2006; Redman 2005; Pickett, Cadenasso, and Grove 2004, 373). Overall, resilience is not an inherent or static property of systems but varies by scale, organizational units, place, and time. This paper provides a critical review of urban scholarship on the relationship between social-ecological diversity and resilience. We identify empirical and theoretical gaps in the urban literature, suggest areas for future research, and develop a research agenda to examine and evaluate the social, institutional, and policy roots of urban ecosystem resilience. We develop the concept of transformative resilience as a heuristic device to examine how different urban ecosystems can adapt, adjust, renew, and transform in response to trauma. Explaining variation in post-trauma urban ecosystem resilience holds tremendous potential for uncovering the causal mechanisms and drivers of political, economic, and social change with policy implications for sustainable development.