[en] Farming in Europe is constantly changing as environmental concerns have increasingly been taken into account since the mid 1980s and emphasis has been put on agri-environmental matters throughout all European countries. For instance, in Wallonia (Belgium), as a result of the provisions of the Government Decree on agri-environmental measures, farmers are increasingly encouraged to adopt environmentally friendly practices such as the creation of grassy headlands in their fields. As European agriculture is changing, tools are needed to monitor the evolution of agricultural practices, to control policy application and to advise farmers. In this framework, we present a new approach to optimise the establishment of grassy headlands in cultivated fields. Using a Geographic Information System (GIS), we identify exact locations where farmers can introduce grassy headlands in accordance with legal specifications and environmental concerns and calculate the total length of grassy headland that farmers can establish considering the features of their farm and parcels and for which they can receive subsidies. It indicates a potential, which could serve as a calculation baseline for an indicator. Wallonia was chosen as study area because a digitised parcel plan has been available from the Integrated Administration and Control System (IACS) since 1997. The methodological approach proposes a new valorisation of this spatial information layer and can be considered as an example of application providing relevant information for several intervention levels: national or regional decisionmakers, advisors and individual farmers. Since all EU Member States had to set up their own GIS-based land parcel system starting in 2005, our approach may be useful as is or in similar applications in other countries. (c) 2006 Elsevier Ltd. All rights reserved.