The JAEA has initiated a project to model the future distribution of radioactivity on a regional scale, beginning with field investigations to acquire the data that are needed to develop conceptual and mathematical migration models of radiocesium’s environmental behavior. The project includes interdisciplinary Japanese teams, as well as international expertise, which is important for ensuring that the project builds on models that have been used in other contaminated environments, and that it benefits from long-term databases from older incidents that can be used to test models’ predictive power.