As a result of the frustration with the dominant "What Works" paradigm of large-scale research-based improvement, practitioners, researchers, foundations, and policymakers are increasingly embracing a set of ideas and practices that can be collectively labeled continuous improvement (CI) methods. This chapter provides a comparative review of these methods, paying particular attention to CI methods' intellectual influences, theories of action, and affordances and challenges in practice. We first map out and explore the shared intellectual forebears that CI methods draw on. We then discuss three kinds of complexity to which CI methods explicitly attend--ambiguity, variability, and interdependence--and how CI methods seek a balance of local and formal knowledge in response to this complexity. We go on to argue that CI methods are generally less attentive to the relational and political dimensions of educational change and that this leads to challenges in practice. We conclude by considering CI methods' aspirations for impact at scale, and offer a number of recommendations to inform future research and practice.