A number of models of sustainable urban form have been promoted but the concept has not been subject to a fundamental review of its theoretical and empirical underpinnings. Sustainable urban form implies an inter-linkage of sound environmental, social and economic foundations. This paper initially focuses on the nature of the economic debate surrounding sustainable urban forms. It then considers the principal elements of urban form - land use patterns, position/ transport infrastructure, density, characteristics of the built environment. From this base it considers the underlying urban economic forces that shape these elements and their impact in turn on the urban economy. The role of transport infrastructure and spatial real estate markets is highlighted in the determination of urban form. The paper suggests an alternative formulation of the approach to urban sustainability that requires as a necessary condition a viable real estate sector with sustainable markets. As a consequence the paper argues the need for policy to understand and shape functional (sub) land use market/ catchment areas.