The risks of the use of nuclear, radiological, biological or chemical (NRBC) weapons are heterogeneous. Each risk has its own implications for developing and deploying any capacity to assist victims of an NRBC event and, in parallel, for the health and security of the people bringing this assistance. At an international level, there are no plans for assisting the victims of an NRBC event which are both adequate and safe. Recognizing the realities of the contexts associated with each risk throws up numerous challenges; such recognition is also a prerequisite for addressing these challenges. The realities that have to be considered relate to: 1. developing, acquiring, training for and planning an NRBC response capacity; 2. deploying a response capacity in an NRBC event; 3. the mandates and policies of international organizations pertaining to NRBC events. The challenges that will pose the greatest difficulty for a humanitarian organization are those for which the solutions are ‘non-buyable’ and which involve making extremely difficult decisions. Attempting to assist victims of an NRBC event without a reality-based approach might generate ineffective and unacceptably dangerous situations for those involved.