This research is motivated by the need to create urban environments that cater to population growth and provide quality of life in ways that limit the detrimental impacts of urban development. The research consists of a review, analysis and critique of attempts to implement sustainability principles through the use of performance assessment tools in the delivery of master planned estates (MPEs) in Australia. At the core of the inquiry is a systematic analysis of sustainability assessment and decision-making tools currently utilised in the MPE development sector, as such tools are primary vehicles for attempting to move sustainability from theory into practice.   The research draws on case study methodology and evaluation studies to develop an analytical framework derived from a critical review of literature on sustainability, sustainability assessment and MPEs. The application of the framework to selected cases studies of existing sustainability assessment tools targeted as MPE development reveals the strengths and weaknesses of tools in terms of their response to sustainability theory, implementation of sustainability assessment methodology, and effectiveness as mechanisms for operationalising sustainability principles in the planning and delivery of MPEs.   The thesis reveals a limited but growing engagement with sustainability in MPE development, and a corresponding emergence of sustainability assessment tools targeted at this scale of development. However, there is little critical interrogation of the integrity and effectiveness of such tools. This thesis shows that current sustainability assessment tools acting in this space are lacking in rigour, transparency and independent verification. They are being utilised by a small subsection of developers who selectively apply assessment to targeted projects. Existing tools thus provide limited opportunity to have a significant impact on sustainability performance across the MPE development sector.   Building on the analysis of existing tools, the thesis proposes guiding principles for the future development and use of assessment tools to more successfully operationalise sustainability in the delivery of MPEs. In examining the implications of the analysis of tools for existing urban policy frameworks, the thesis argues that effective sustainability assessment of MPE development requires an increased role for government to either develop standards to ensure the integrity of industry and independent tools and integration with development approval processes, or to develop its own mechanisms for sustainability assessment in development approval