Effective development of city-regions is a major challenge and requires reliable and pertinent indicators to guide planners’ actions and monitor progress. The large number of ‘green city’ and ‘sustainable city’ indices that are flourishing today differ in key aspects of methodology and definition, in part because there is no consensus on the main attributes of a sustainable city and the appropriate metrics. While a range of indicators and reporting systems may be an asset reflecting the unique needs of each community, it also presents a significant challenge to designing a common or standardised sustainability indicator framework and developing database and reporting protocols. Within the framework of the Urban environmental Accords, the objective of this paper was to examine the opportunities for developing a global consensus on an Urban environmental Index to assess the environmental performance of cities. We analysed a variety of conceptual and actual sustainability and environmental reporting systems at the national and community/municipal level and evaluated their strengths and weaknesses in the face of current challenges.