This report examines the current state of knowledge about green growth in cities and outlines the key research questions and protocols that will guide the OECD Green Cities programme. It builds the case for an urban green growth agenda by examining the economic and environmental conditions that have pushed the green growth agenda to the forefront of policy debate and assessing the critical role of cities in advancing green growth. Section 1 lays the context for the paper, examining why green growth is important and how it can be defined in an urban context. Section 2 focuses on policies and tools that enable the transition to green growth in cities. It concludes with a proposal for a policy framework for an urban green growth agenda that is based on a set of hypotheses of desirable economic scenarios. Section 3 examines the main challenges to advancing an urban green growth agenda. It explores the roles that multi-level governance, measuring and monitoring tools and finance must play in delivering green growth in cities. The report concludes with suggestions for future research, including recommendations on how national policymakers responsible for regional and urban policies can advance an urban green growth agenda.