The dramatic changes in land use observed in Europe in the last fifty years have generally resulted in improvement of human welfare and economic development. On the other hand, they have caused serious environmental problems. There is therefore a need for approaches that help to understand in an integrative way the economic, environmental and societal impacts that land use changes have on sustainability. Sustainability Impact Assessment (SIA), which assesses the impact of policies on sustainability, addresses this challenge. SIA partly builds on the concept of the multifunctionality of land which helps to deal with the complexity of interactions between different land uses, their temporal and spatial changes, and finally how policies might steer those changes towards sustainability. Following this need for true integration of economic, environmental and societal issues across policy areas at a meaningful spatial scale, an interdisciplinary team in the SENSOR project has developed an innovative conceptual framework to assess the impact of policies on land sustainability at various levels of spatial aggregation i.e. the Land Use Functions (LUFs) framework. LUFs are the goods and services provided by the different land uses that summarise the most relevant economic, environmental and societal issues of a region. The LUFs framework integrates the changes observed in a large set of impact indicators into nine Land Use Functions (LUFs), which are balanced among the three pillars of sustainability. The LUFs framework makes it possible for policy makers, scientists and stakeholders to identify at a glance those functions of the land which are hindered or enhanced under various scenarios of land use change, and makes it possible to explore the trade-offs between them. The LUFs framework allows therefore the building of assessment across disciplines, sectors and the three sustainability dimensions. It has proved to be very helpful for the systematisation of relevant sustainability indicators within SENSOR and is intended to be further used in other projects as a tool for Sustainability Impact Assessment. The rationale leading to the LUFs concept, its definition and the conceptual framework is described in this chapter. We conclude that the concept of LUFs allows users to make explicit the analytical links between multifunctional land use and sustainable development, and therefore to look at multifunctionality as a way towards sustainability.