With the ICRP recommendations Publications 103, 109 and 111 (ICRP, 2007; ICRP 2009a,2009b), new concepts and quantities have been introduced into emergency management andrehabilitation. Two of them will possibly influence national procedures, but for sure theywill influence countermeasure simulation approaches: 1. The concept of a “reference level”for emergency and existing controllable exposure situations that represents the level ofdose or risk, above which it is judged to be inappropriate to plan to allow exposures tooccur, and for which therefore protective actions should be planned in advance. 2. Whendeciding on the optimum course of protective actions, all exposure pathways and allrelevant actions have to be taken into account. The major changes for the simulationmodels result from the second recommendation that all exposure pathways must be consideredwhen deciding on protective actions. So far all countermeasure simulations in the earlyphase of an emergency are carried out by considering individual countermeasures such assheltering or evacuation, if some dose limit for the respective action is exceeded. Thisapproach has to be changed and strategies of several countermeasures analysed andsimulated with the ultimate goal not to exceed the reference level over a given timeperiod, typically one year.