Agricultural policy makers aim to combine strong economic performance with a sustainable use of natural resources. An important step is to move from trying to define sustainability towards developing concrete tools for measuring and promoting achievements in sustainability. Hence, sustainability assessment is inevitably based on strong simplifications both of the theoretical paradigm and of the characteristics of systems of concern. The most known approaches to assess sustainability performance are burden orientated : they assess the costs or potential harm of resource use. These burden-oriented approaches focus on the level of environmental impacts caused by an economic activity compared to another set of environmental impacts, while value-oriented impact assessment analyses how much value has been created with this set of environmental impacts as compared with the use of these resources by other companies. In this paper, an outline of the possibilities and limitations of value-oriented methods to assess farm sustainability will be discussed.