[en] An important task of emergency planning is to determine countermeasures during different time phases of an airborne plume. For this purpose a Catalogue of Countermeasures was created. The purpose of the catalogue it to be a primary guide for experts of competent governmental and state authorities as well as for persons belonging to the respective advisory and supporting panel, who have to assess and evaluate the situation and to select protection measures in the case of a nuclear event with radiological consequences off-site. Since radiation is generally not directly measurable, it is, for practical purposes, not the radiation dose itself but the derived measurable quantities that are used for decision-making. On this basis the catalogue is a tool for deciding on the initiation of countermeasures based on Operational Intervention Levels. (author)