Increasing concern about the effects of agriculture on the environment has drawn attention to the inadequate scientific base on which many policy decisions are made. Decisions on how soil should best be protected from erosion demand knowledge of the risk of erosion and of the relative effectiveness of different conservation measures. Process-based erosion models are designed to provide this information. This paper outlines one such model, the European Soil Erosion Model (EUROSEM), which is being developed jointly by scientists from ten European countries. The model incorporates some of the best process-based erosion research being carried out in Europe and, compared with other similar models, contains novel features in the way rill–interrill interactions and the role of vegetation are described. Tests of the model in the UK show that it performs rationally and gives reasonable predictions of storm soil loss and runoff. Some examples of how the model might be used to evaluate conservation measures are provided.