As the global population grows increasingly urbanized, city governments will assume ever-greater responsibility for addressing the challenges of poverty, inequality, and environmental sustainability. To meet these challenges effectively, city leaders must base their efforts on good data and reliable evidence. This paper develops a framework for understanding the conditions under which city leaders access, analyze, and apply data to solve problems. We also suggest how the new UN Sustainable Development Goals can help overcome the institutional constraints and competing incentives that cities face in using data to drive decisionmaking for sustainable development.