Rising concern about agricultural non-print water pollution has led to the proposal of many regulatory measures. Agri-environmental programmes have been implemented in the different EU Member States according to the Commission regulation 2078/92. Best management practices, one of the most popular tools, have rarely been assessed in a fully satisfying way. Therefore, the main objective of this project is to provide planners in charge of the implementation of BMPs in the field of combating diffusion pollution either at a national or local scale, with both a guideline allowing the definition of critical areas on which efforts should be place in priority, and a selection grid permitting the assessment of BMPs in a three-dimensional space defined by environmental effectiveness, associated economic costs and social acceptability by farmers and land managers. Expectedd results should contribute to help Member States choosing the most appropriate measures and ways for an efficient implementation of BMPs, with the support of scientifically validated technical and economic recommendations.