INTRODUCTION A significant milestone was recently passed, with the majority of humankind now living in cities. For the first time in the history of our species, the immediate human environment will primarily be the built environment. Accelerating urbanization does not change the fact, however, that human beings ultimately remain dependent on the environment. Cities and their growth will necessarily become major drivers of environmental and ecological change, and global sustainable development will therefore be inextricably tied to the development of cities. As a global term, ‘sustainability’ attempts to balance myriad social, economic, and environmental factors, and is so complex in its application that a simple directive is useful to condense the discussion. As Wheeler succinctly describes it, sustainable urban development ‘improves the long term social and ecological health of cities and towns.’ 1 As cities are the major consumers of natural resources and the major producers of pollution and waste, it follows that if they can be designed and managed so that resource use and pollution are reduced, a major contribution to the solution of the global problem can be achieved.2 Urban areas will always be net consumers of resources, and major degraders of the environment, however, it may be possible to move toward a greater degree of sustainability. The question that this paper will address is whether the spatial built form of a city can affect its sustainability, what this relationship may entail, and what metrics might exist to help guide the growth of cities. Different points of view will be explored, illustrating the lack of consensus that exists on certain ‘truths.’ The relative sustainability of, for example, high and low urban densities is still disputed. Certain urban forms may appear to be more sustainable in some respects, for example in reducing travel, but detrimental in others, perhaps in harming the environment or producing social disparities. Some forms may be sustainable in a local sense, but not on a larger scale. If advances in urban sustainability are to be made, then a connection between urban form and a range of elements needs to be established. How are issues of urban size, shape, density, and compactness, urban block layout and size, housing type, green space distribution, to be guided along a sustainable path? What is in fact sustainable urban form? How can it be achieved? I propose to investigate many of these questions by researching current debates and points of view, together with evaluating a popular and accessible urban sustainability metric to see if it can meaningfully guide sustainable urban form. LEED for Neighbourhood Development is a planning metric for urban sustainability and contains a normative set of ‘building blocks’ for sustainable urban form, in the form of a checklist of components. A review of this planning metric for community sustainability will be undertaken, as it relates to urban form, as well as inherent biases that may exist. Strengths and weaknesses of this system will be evaluated, with examples of designed and built communities broadly evaluated. The issue of how LEED-ND may be able to affect urban form will be explored, and whether it has a deep enough reach to be transformative. How this rating system can be used to measure and compare urban forms will be explored, as well as the ability of this rating system to encompass balanced social, economic, and environmental factors. A key issue is whether this, and other rating systems, can truly reverse dominant trends, or whether they are doomed to create ‘sustainable islands in seas of unsustainability.’3