This paper provides the key elements to develop an integrated approach for measuring and monitoring city performance globally. The paper reviews the role of cities and why indicators are important. Then it discusses past approaches to city indicators and the systems developed to date, including the World Bank's initiatives. After identifying the strengths and weaknesses of past experiences, it discusses the characteristics of optimal indicators. The paper concludes with a proposed plan to develop standardized indicators that emphasize the importance of indicators that are measurable, replicable, potentially predictive, and most important, consistent and comparable over time and across cities. As an innovative characteristic, the paper includes subjective measures in city indicators, such as well-being, happy citizens, and trust.