Abstract: Green is not alone in contending that `̀ environmental c̀rises' require fundamental changes in the socio-technological structure of the way we live and work.''(1) For those concerned with sustainability, the idea of transitionöof substantial change and movement from one state to anotheröhas powerful normative attractions. If `we' can steer change, shape future development, and manage movement in desired directions, perhaps `we' can make the environment a better and more sustainable place in which to live. But how so to do? In a manifestly complex world dominated by hegemonic ideologies of neoliberal capitalism, global finance, and commodity flows is it really possible to intervene and deliberately shift technologies, practices, and social arrangementsönot to mention their systemic interaction and interdependenciesöonto an altogether different, altogether more sustainable track? Across the board there is growing recognition of the holistic, unavoidably interrelated nature of contemporary environmental problems and of the need for fresh approaches and forms of governance capable of engaging with complex challenges of this kind. Theories and models of sustainable transition management, derived from a blend of academic traditions in innovation, history, and technology, appear to fit this bill and it is no wonder that they are now catching on across a number of policy domains. In the Netherlands, government-sponsored programmes have explicitly adopted methods of `transition management' (Kemp and Loorbach, 2006) and in the UK, the policy relevance of similar theories and methods is being explored and actively promoted through projects and events like those supported by the ESRC's Sustainable Technologies Programme. Academically, and in just a few years, there has been rapid growth in the transition management literature and in the appeal of approaches characterised by an alluring combination of agency, complexity, uncertainty, and optimism. We do not intend to provide a thorough review or critique of what is in any case a burgeoning and quickly evolving literature, but at a time when the notion of transition management is capturing so much attention it is as well to reflect on the distinctive features of this particular policy innovation. With this limited aim in mind, we offer some cautionary comments and identify a handful of questions that deserve more explicit attention. The notion of transition is firmly rooted in traditions of system thinking which highlight the coevolution of the social and the technical and which seek to understand and analyse the emergence, transformation, and decay of sociotechnical systems. Much of the `systems in transition' literature makes use of Rip and Kemp's (1998) `multilevel' model of innovation which distinguishes between the macrolevel of the sociotechnical landscape, the mesolevel regime, and the microlevel niche. The key Commentary Environment and Planning A 2007, volume 39, pages 763 ^ 770