The built environment is responsible for around half of total greenhouse gas emissions with the majority of emissions produced during the building lifecycle. As such the property sector has considerable potential to reduce lifecycle emissions and can contribute in mitigating global warming. Our existing conceptual understanding of sustainability is variable to the point of being disjointed and ambiguous. An excess of terms is used in connection with sustainability and property, such as ecologic, green, Gaian which fall in and out of use over time. The question is; do these terms mean the same thing or are they different? Moreover do firms in the Australian property sector demonstrate a clear conceptual understanding of sustainability or; are they confused? The outcome of ambiguous ideas and a lack of insight is that the property sector will be unlikely to bring about ìòsustainabilityí adeptly or even at all with more onerous costs for society. Published information on property company websites regarding sustainability was analysed to address the questions; (a) what is the conceptual understanding of sustainability within the top 20 Australian property firms and, (b) what is the implication of this level of conceptual understanding with regards to delivering sustainability